From 4a72736d1993d5702d074ea1a92e584633b20f54 Mon Sep 17 00:00:00 2001
From: Michael Lohmann <git@lohmann.sh>
Date: Tue, 30 Sep 2025 21:53:20 +0200
Subject: [PATCH 01/13] builtin/reflog: respect user config in "write"
 subcommand

The reflog write recognizes only GIT_COMMITTER_NAME and
GIT_COMMITTER_EMAIL environment variables, but forgot to honor the
user.name and user.email configuration variables, due to lack of
repo_config() call to grab these values from the configuration files.

The test suite sets these variables, so this behavior was unnoticed.

Ensure that the reflog write also uses the values of user.name and
user.email if set in the Git configuration.

Co-authored-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Michael Lohmann <git@lohmann.sh>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 builtin/reflog.c        |  2 ++
 t/t1421-reflog-write.sh | 36 ++++++++++++++++++++++++++++++++++++
 2 files changed, 38 insertions(+)

diff --git a/builtin/reflog.c b/builtin/reflog.c
index a1b4e02204178f..a17b5fa69e4cb1 100644
--- a/builtin/reflog.c
+++ b/builtin/reflog.c
@@ -415,6 +415,8 @@ static int cmd_reflog_write(int argc, const char **argv, const char *prefix,
 	const char *ref, *message;
 	int ret;
 
+	repo_config(repo, git_ident_config, NULL);
+
 	argc = parse_options(argc, argv, prefix, options, reflog_write_usage, 0);
 	if (argc != 4)
 		usage_with_options(reflog_write_usage, options);
diff --git a/t/t1421-reflog-write.sh b/t/t1421-reflog-write.sh
index 46df64c1761b40..603ec3f6ed7ace 100755
--- a/t/t1421-reflog-write.sh
+++ b/t/t1421-reflog-write.sh
@@ -108,6 +108,42 @@ test_expect_success 'simple writes' '
 	)
 '
 
+test_expect_success 'uses user.name and user.email config' '
+	test_when_finished "rm -rf repo" &&
+	git init repo &&
+	(
+		cd repo &&
+		test_commit initial &&
+		COMMIT_OID=$(git rev-parse HEAD) &&
+
+		sane_unset GIT_COMMITTER_NAME &&
+		sane_unset GIT_COMMITTER_EMAIL &&
+		git config --local user.name "Author" &&
+		git config --local user.email "a@uth.or" &&
+		git reflog write refs/heads/something $ZERO_OID $COMMIT_OID first &&
+		test_reflog_matches . refs/heads/something <<-EOF
+		$ZERO_OID $COMMIT_OID Author <a@uth.or> $GIT_COMMITTER_DATE	first
+		EOF
+	)
+'
+
+test_expect_success 'environment variables take precedence over config' '
+	test_when_finished "rm -rf repo" &&
+	git init repo &&
+	(
+		cd repo &&
+		test_commit initial &&
+		COMMIT_OID=$(git rev-parse HEAD) &&
+
+		git config --local user.name "Author" &&
+		git config --local user.email "a@uth.or" &&
+		git reflog write refs/heads/something $ZERO_OID $COMMIT_OID first &&
+		test_reflog_matches . refs/heads/something <<-EOF
+		$ZERO_OID $COMMIT_OID $SIGNATURE	first
+		EOF
+	)
+'
+
 test_expect_success 'can write to root ref' '
 	test_when_finished "rm -rf repo" &&
 	git init repo &&

From 351c6e719ae9c5b97506dde6bc287408b80e87e4 Mon Sep 17 00:00:00 2001
From: Karthik Nayak <karthik.188@gmail.com>
Date: Wed, 1 Oct 2025 14:17:29 +0200
Subject: [PATCH 02/13] refs/ref-cache: fix SEGFAULT when seeking in empty
 directories

The 'cache_ref_iterator_seek()' function is used to seek the
`ref_iterator` to the desired reference in the ref-cache mechanism. We
use the seeking functionality to implement the '--start-after' flag in
'git-for-each-ref(1)'.

When using the files-backend with packed-refs, it is possible that some
of the refs directories are empty. For e.g. just after repacking, the
'refs/heads' directory would be empty. The ref-cache seek mechanism,
doesn't take this into consideration when descending into a
subdirectory, and makes an out of bounds access, causing SEGFAULT as we
try to access entries within the directory. Fix this by breaking out of
the loop when we enter an empty directory.

Since we start with the base directory of 'refs/' which is never empty,
it is okay to perform this check after the first iteration in the
`do..while` clause.

Add tests which simulate this behavior and also provide coverage over
using the feature over packed-refs.

Helped-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Karthik Nayak <karthik.188@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 refs/ref-cache.c               |  2 +-
 t/t6302-for-each-ref-filter.sh | 65 ++++++++++++++++++++++++++++++++++
 2 files changed, 66 insertions(+), 1 deletion(-)

diff --git a/refs/ref-cache.c b/refs/ref-cache.c
index c180e0aad74e87..e5e5df16d85e40 100644
--- a/refs/ref-cache.c
+++ b/refs/ref-cache.c
@@ -539,7 +539,7 @@ static int cache_ref_iterator_seek(struct ref_iterator *ref_iterator,
 				 */
 				break;
 			}
-		} while (slash);
+		} while (slash && dir->nr);
 	}
 
 	return 0;
diff --git a/t/t6302-for-each-ref-filter.sh b/t/t6302-for-each-ref-filter.sh
index 9b80ea1e3b7414..7f060d97bf509c 100755
--- a/t/t6302-for-each-ref-filter.sh
+++ b/t/t6302-for-each-ref-filter.sh
@@ -754,4 +754,69 @@ test_expect_success 'start after used with custom sort order' '
 	test_cmp expect actual
 '
 
+test_expect_success 'start after with packed refs' '
+	test_when_finished "rm -rf repo" &&
+	git init repo &&
+	(
+		cd repo &&
+		test_commit default &&
+
+		git update-ref --stdin <<-\EOF &&
+		create refs/heads/branch @
+		create refs/heads/side @
+		create refs/odd/spot @
+		create refs/tags/one @
+		create refs/tags/two @
+		commit
+		EOF
+
+		cat >expect <<-\EOF &&
+		refs/tags/default
+		refs/tags/one
+		refs/tags/two
+		EOF
+
+		git pack-refs --all &&
+		git for-each-ref --format="%(refname)" --start-after=refs/odd/spot >actual &&
+		test_cmp expect actual
+	)
+'
+
+test_expect_success 'start after with packed refs and some loose refs' '
+	test_when_finished "rm -rf repo" &&
+	git init repo &&
+	(
+		cd repo &&
+		test_commit default &&
+
+		git update-ref --stdin <<-\EOF &&
+		create refs/heads/branch @
+		create refs/heads/side @
+		create refs/odd/spot @
+		create refs/tags/one @
+		create refs/tags/two @
+		commit
+		EOF
+
+		git pack-refs --all &&
+
+		git update-ref --stdin <<-\EOF &&
+		create refs/heads/foo @
+		create refs/odd/tee @
+		commit
+		EOF
+
+		cat >expect <<-\EOF &&
+		refs/odd/tee
+		refs/tags/default
+		refs/tags/one
+		refs/tags/two
+		EOF
+
+
+		git for-each-ref --format="%(refname)" --start-after=refs/odd/spot >actual &&
+		test_cmp expect actual
+	)
+'
+
 test_done

From fdd21ba116551efb07e784f138d090917b7e70ad Mon Sep 17 00:00:00 2001
From: M Hickford <mirth.hickford@gmail.com>
Date: Wed, 1 Oct 2025 20:56:49 +0000
Subject: [PATCH 03/13] docs/gitcredentials: describe URL prefix matching

Documentation was inaccurate since 9a121b0d226 (credential: handle
`credential.<partial-URL>.<key>` again, 2020-04-24)

Add tests for documented behaviour.

Signed-off-by: M Hickford <mirth.hickford@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 Documentation/gitcredentials.txt | 15 +++++++--------
 t/t0300-credentials.sh           | 19 +++++++++++++++----
 2 files changed, 22 insertions(+), 12 deletions(-)

diff --git a/Documentation/gitcredentials.txt b/Documentation/gitcredentials.txt
index 35a7452c8fe3cc..931a33f8385830 100644
--- a/Documentation/gitcredentials.txt
+++ b/Documentation/gitcredentials.txt
@@ -133,9 +133,8 @@ pattern in the config file. For example, if you have this in your config file:
 	username = foo
 --------------------------------------
 
-then we will match: both protocols are the same, both hosts are the same, and
-the "pattern" URL does not care about the path component at all. However, this
-context would not match:
+then we will match: both protocols are the same and both hosts are the same.
+However, this context would not match:
 
 --------------------------------------
 [credential "https://kernel.org"]
@@ -149,11 +148,11 @@ match: Git compares the protocols exactly.  However, you may use wildcards in
 the domain name and other pattern matching techniques as with the `http.<URL>.*`
 options.
 
-If the "pattern" URL does include a path component, then this too must match
-exactly: the context `https://example.com/bar/baz.git` will match a config
-entry for `https://example.com/bar/baz.git` (in addition to matching the config
-entry for `https://example.com`) but will not match a config entry for
-`https://example.com/bar`.
+If the "pattern" URL does include a path component, then this must match
+as a prefix path: the context `https://example.com/bar` will match a config
+entry for `https://example.com/bar/baz.git` but will not match a config entry for
+`https://example.com/other/repo.git` or `https://example.com/barry/repo.git`
+(even though it is a string prefix).
 
 
 CONFIGURATION OPTIONS
diff --git a/t/t0300-credentials.sh b/t/t0300-credentials.sh
index cb3a85c7ff1bcc..07aa834d33e248 100755
--- a/t/t0300-credentials.sh
+++ b/t/t0300-credentials.sh
@@ -991,18 +991,24 @@ test_expect_success 'url parser not confused by encoded markers' '
 
 test_expect_success 'credential config with partial URLs' '
 	echo "echo password=yep" | write_script git-credential-yep &&
-	test_write_lines url=https://user@example.com/repo.git >stdin &&
+	test_write_lines url=https://user@example.com/org/repo.git >stdin &&
 	for partial in \
 		example.com \
+		example.com/org/repo.git \
 		user@example.com \
+		user@example.com/org/repo.git \
 		https:// \
 		https://example.com \
 		https://example.com/ \
+		https://example.com/org \
+		https://example.com/org/ \
+		https://example.com/org/repo.git \
 		https://user@example.com \
 		https://user@example.com/ \
-		https://example.com/repo.git \
-		https://user@example.com/repo.git \
-		/repo.git
+		https://user@example.com/org \
+		https://user@example.com/org/ \
+		https://user@example.com/org/repo.git \
+		/org/repo.git
 	do
 		git -c credential.$partial.helper=yep \
 			credential fill <stdin >stdout &&
@@ -1012,7 +1018,12 @@ test_expect_success 'credential config with partial URLs' '
 
 	for partial in \
 		dont.use.this \
+		example.com/o \
+		user@example.com/o \
 		http:// \
+		https://example.com/o \
+		https://user@example.com/o \
+		/o \
 		/repo
 	do
 		git -c credential.$partial.helper=yep \

From c184795fc0eaf660b4fc06e7ee63aa9c136ff1aa Mon Sep 17 00:00:00 2001
From: Patrick Steinhardt <ps@pks.im>
Date: Thu, 2 Oct 2025 09:29:26 +0200
Subject: [PATCH 04/13] meson: add infrastructure to build internal Rust
 library

Add the infrastructure into Meson to build an internal Rust library.
Building the Rust parts of Git are for now entirely optional, as they
are mostly intended as a test balloon for both Git developers, but also
for distributors of Git. So for now, they may contain:

  - New features that are not mission critical to Git and that users can
    easily live without.

  - Alternative implementations of small subsystems.

If these test balloons are successful, we will eventually make Rust a
mandatory dependency for our build process in Git 3.0.

The availability of a Rust toolchain will be auto-detected by Meson at
setup time. This behaviour can be tweaked via the `-Drust=` feature
toggle.

Next to the linkable Rust library, also wire up tests that can be
executed via `meson test`. This allows us to use the native unit testing
capabilities of Rust.

Note that the Rust edition is currently set to 2018. This edition is
supported by Rust 1.49, which is the target for the upcoming gcc-rs
backend. For now we don't use any features of Rust that would require a
newer version, so settling on this old version makes sense so that
gcc-rs may become an alternative backend for compiling Git. If we _do_
want to introduce features that were added in more recent editions of
Rust though we should reevaluate that choice.

Inspired-by: Ezekiel Newren <ezekielnewren@gmail.com>
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 Cargo.toml         |  9 +++++++++
 meson.build        | 10 +++++++++-
 meson_options.txt  |  2 ++
 src/cargo-meson.sh | 32 ++++++++++++++++++++++++++++++++
 src/lib.rs         |  0
 src/meson.build    | 40 ++++++++++++++++++++++++++++++++++++++++
 6 files changed, 92 insertions(+), 1 deletion(-)
 create mode 100644 Cargo.toml
 create mode 100755 src/cargo-meson.sh
 create mode 100644 src/lib.rs
 create mode 100644 src/meson.build

diff --git a/Cargo.toml b/Cargo.toml
new file mode 100644
index 00000000000000..45c9b34981abb3
--- /dev/null
+++ b/Cargo.toml
@@ -0,0 +1,9 @@
+[package]
+name = "gitcore"
+version = "0.1.0"
+edition = "2018"
+
+[lib]
+crate-type = ["staticlib"]
+
+[dependencies]
diff --git a/meson.build b/meson.build
index e8ec0eca1650a5..234a9e9d6fd461 100644
--- a/meson.build
+++ b/meson.build
@@ -220,7 +220,7 @@ project('git', 'c',
   # learned to define __STDC_VERSION__ with C11 and later. We thus require
   # GNU C99 and fall back to C11. Meson only learned to handle the fallback
   # with version 1.3.0, so on older versions we use GNU C99 unconditionally.
-  default_options: meson.version().version_compare('>=1.3.0') ? ['c_std=gnu99,c11'] : ['c_std=gnu99'],
+  default_options: meson.version().version_compare('>=1.3.0') ? ['rust_std=2018', 'c_std=gnu99,c11'] : ['rust_std=2018', 'c_std=gnu99'],
 )
 
 fs = import('fs')
@@ -1702,6 +1702,13 @@ version_def_h = custom_target(
 )
 libgit_sources += version_def_h
 
+cargo = find_program('cargo', dirs: program_path, native: true, required: get_option('rust'))
+rust_option = get_option('rust').disable_auto_if(not cargo.found())
+if rust_option.allowed()
+  subdir('src')
+  libgit_c_args += '-DWITH_RUST'
+endif
+
 libgit = declare_dependency(
   link_with: static_library('git',
     sources: libgit_sources,
@@ -2239,6 +2246,7 @@ summary({
   'pcre2': pcre2,
   'perl': perl_features_enabled,
   'python': target_python.found(),
+  'rust': rust_option.allowed(),
 }, section: 'Auto-detected features', bool_yn: true)
 
 summary({
diff --git a/meson_options.txt b/meson_options.txt
index 1668f260a1858c..143dee9237cb41 100644
--- a/meson_options.txt
+++ b/meson_options.txt
@@ -71,6 +71,8 @@ option('zlib_backend', type: 'combo', choices: ['auto', 'zlib', 'zlib-ng'], valu
 # Build tweaks.
 option('breaking_changes', type: 'boolean', value: false,
   description: 'Enable upcoming breaking changes.')
+option('rust', type: 'feature', value: 'auto',
+  description: 'Enable building with Rust.')
 option('macos_use_homebrew_gettext', type: 'boolean', value: true,
   description: 'Use gettext from Homebrew instead of the slightly-broken system-provided one.')
 
diff --git a/src/cargo-meson.sh b/src/cargo-meson.sh
new file mode 100755
index 00000000000000..99400986d93509
--- /dev/null
+++ b/src/cargo-meson.sh
@@ -0,0 +1,32 @@
+#!/bin/sh
+
+if test "$#" -lt 2
+then
+	exit 1
+fi
+
+SOURCE_DIR="$1"
+BUILD_DIR="$2"
+BUILD_TYPE=debug
+
+shift 2
+
+for arg
+do
+	case "$arg" in
+	--release)
+		BUILD_TYPE=release;;
+	esac
+done
+
+cargo build --lib --quiet --manifest-path="$SOURCE_DIR/Cargo.toml" --target-dir="$BUILD_DIR" "$@"
+RET=$?
+if test $RET -ne 0
+then
+	exit $RET
+fi
+
+if ! cmp "$BUILD_DIR/$BUILD_TYPE/libgitcore.a" "$BUILD_DIR/libgitcore.a" >/dev/null 2>&1
+then
+	cp "$BUILD_DIR/$BUILD_TYPE/libgitcore.a" "$BUILD_DIR/libgitcore.a"
+fi
diff --git a/src/lib.rs b/src/lib.rs
new file mode 100644
index 00000000000000..e69de29bb2d1d6
diff --git a/src/meson.build b/src/meson.build
new file mode 100644
index 00000000000000..c8d874b2106176
--- /dev/null
+++ b/src/meson.build
@@ -0,0 +1,40 @@
+libgit_rs_sources = [
+  'lib.rs',
+]
+
+# Unfortunately we must use a wrapper command to move the output file into the
+# current build directory. This can fixed once `cargo build --artifact-dir`
+# stabilizes. See https://github.com/rust-lang/cargo/issues/6790 for that
+# effort.
+cargo_command = [
+  shell,
+  meson.current_source_dir() / 'cargo-meson.sh',
+  meson.project_source_root(),
+  meson.current_build_dir(),
+]
+if get_option('buildtype') == 'release'
+  cargo_command += '--release'
+endif
+
+libgit_rs = custom_target('git_rs',
+  input: libgit_rs_sources + [
+    meson.project_source_root() / 'Cargo.toml',
+  ],
+  output: 'libgitcore.a',
+  command: cargo_command,
+)
+libgit_dependencies += declare_dependency(link_with: libgit_rs)
+
+if get_option('tests')
+  test('rust', cargo,
+    args: [
+      'test',
+      '--manifest-path',
+      meson.project_source_root() / 'Cargo.toml',
+      '--target-dir',
+      meson.current_build_dir() / 'target',
+    ],
+    timeout: 0,
+    protocol: 'rust',
+  )
+endif

From f2301be0765ef1baad163edcae96df92c5e05074 Mon Sep 17 00:00:00 2001
From: Patrick Steinhardt <ps@pks.im>
Date: Thu, 2 Oct 2025 09:29:27 +0200
Subject: [PATCH 05/13] Makefile: reorder sources after includes

In an upcoming change we'll make some of the sources compile
conditionally based on whether or not `WITH_RUST` is defined. To let
developers specify that flag in their "config.mak" we'll thus have to
reorder our sources so that they come after the include of that file.

Do so.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 Makefile | 176 +++++++++++++++++++++++++++----------------------------
 1 file changed, 88 insertions(+), 88 deletions(-)

diff --git a/Makefile b/Makefile
index 555b7f4dc3c0e1..7e52625d755061 100644
--- a/Makefile
+++ b/Makefile
@@ -919,6 +919,94 @@ LIB_FILE = libgit.a
 XDIFF_LIB = xdiff/lib.a
 REFTABLE_LIB = reftable/libreftable.a
 
+# xdiff and reftable libs may in turn depend on what is in libgit.a
+GITLIBS = common-main.o $(LIB_FILE) $(XDIFF_LIB) $(REFTABLE_LIB) $(LIB_FILE)
+EXTLIBS =
+
+GIT_USER_AGENT = git/$(GIT_VERSION)
+
+ifeq ($(wildcard sha1collisiondetection/lib/sha1.h),sha1collisiondetection/lib/sha1.h)
+DC_SHA1_SUBMODULE = auto
+endif
+
+# Set CFLAGS, LDFLAGS and other *FLAGS variables. These might be
+# tweaked by config.* below as well as the command-line, both of
+# which'll override these defaults.
+# Older versions of GCC may require adding "-std=gnu99" at the end.
+CFLAGS = -g -O2 -Wall
+LDFLAGS =
+CC_LD_DYNPATH = -Wl,-rpath,
+BASIC_CFLAGS = -I.
+BASIC_LDFLAGS =
+
+# library flags
+ARFLAGS = rcs
+PTHREAD_CFLAGS =
+
+# For the 'sparse' target
+SPARSE_FLAGS ?= -std=gnu99 -D__STDC_NO_VLA__
+SP_EXTRA_FLAGS =
+
+# For informing GIT-BUILD-OPTIONS of the SANITIZE=leak,address targets
+SANITIZE_LEAK =
+SANITIZE_ADDRESS =
+
+# For the 'coccicheck' target
+SPATCH_INCLUDE_FLAGS = --all-includes
+SPATCH_FLAGS =
+SPATCH_TEST_FLAGS =
+
+# If *.o files are present, have "coccicheck" depend on them, with
+# COMPUTE_HEADER_DEPENDENCIES this will speed up the common-case of
+# only needing to re-generate coccicheck results for the users of a
+# given API if it's changed, and not all files in the project. If
+# COMPUTE_HEADER_DEPENDENCIES=no this will be unset too.
+SPATCH_USE_O_DEPENDENCIES = YesPlease
+
+# Set SPATCH_CONCAT_COCCI to concatenate the contrib/cocci/*.cocci
+# files into a single contrib/cocci/ALL.cocci before running
+# "coccicheck".
+#
+# Pros:
+#
+# - Speeds up a one-shot run of "make coccicheck", as we won't have to
+#   parse *.[ch] files N times for the N *.cocci rules
+#
+# Cons:
+#
+# - Will make incremental development of *.cocci slower, as
+#   e.g. changing strbuf.cocci will re-run all *.cocci.
+#
+# - Makes error and performance analysis harder, as rules will be
+#   applied from a monolithic ALL.cocci, rather than
+#   e.g. strbuf.cocci. To work around this either undefine this, or
+#   generate a specific patch, e.g. this will always use strbuf.cocci,
+#   not ALL.cocci:
+#
+#	make contrib/coccinelle/strbuf.cocci.patch
+SPATCH_CONCAT_COCCI = YesPlease
+
+# Rebuild 'coccicheck' if $(SPATCH), its flags etc. change
+TRACK_SPATCH_DEFINES =
+TRACK_SPATCH_DEFINES += $(SPATCH)
+TRACK_SPATCH_DEFINES += $(SPATCH_INCLUDE_FLAGS)
+TRACK_SPATCH_DEFINES += $(SPATCH_FLAGS)
+TRACK_SPATCH_DEFINES += $(SPATCH_TEST_FLAGS)
+GIT-SPATCH-DEFINES: FORCE
+	@FLAGS='$(TRACK_SPATCH_DEFINES)'; \
+	    if test x"$$FLAGS" != x"`cat GIT-SPATCH-DEFINES 2>/dev/null`" ; then \
+		echo >&2 "    * new spatch flags"; \
+		echo "$$FLAGS" >GIT-SPATCH-DEFINES; \
+            fi
+
+include config.mak.uname
+-include config.mak.autogen
+-include config.mak
+
+ifdef DEVELOPER
+include config.mak.dev
+endif
+
 GENERATED_H += command-list.h
 GENERATED_H += config-list.h
 GENERATED_H += hook-list.h
@@ -1387,94 +1475,6 @@ CLAR_TEST_OBJS += $(UNIT_TEST_DIR)/unit-test.o
 
 UNIT_TEST_OBJS += $(UNIT_TEST_DIR)/test-lib.o
 
-# xdiff and reftable libs may in turn depend on what is in libgit.a
-GITLIBS = common-main.o $(LIB_FILE) $(XDIFF_LIB) $(REFTABLE_LIB) $(LIB_FILE)
-EXTLIBS =
-
-GIT_USER_AGENT = git/$(GIT_VERSION)
-
-ifeq ($(wildcard sha1collisiondetection/lib/sha1.h),sha1collisiondetection/lib/sha1.h)
-DC_SHA1_SUBMODULE = auto
-endif
-
-# Set CFLAGS, LDFLAGS and other *FLAGS variables. These might be
-# tweaked by config.* below as well as the command-line, both of
-# which'll override these defaults.
-# Older versions of GCC may require adding "-std=gnu99" at the end.
-CFLAGS = -g -O2 -Wall
-LDFLAGS =
-CC_LD_DYNPATH = -Wl,-rpath,
-BASIC_CFLAGS = -I.
-BASIC_LDFLAGS =
-
-# library flags
-ARFLAGS = rcs
-PTHREAD_CFLAGS =
-
-# For the 'sparse' target
-SPARSE_FLAGS ?= -std=gnu99 -D__STDC_NO_VLA__
-SP_EXTRA_FLAGS =
-
-# For informing GIT-BUILD-OPTIONS of the SANITIZE=leak,address targets
-SANITIZE_LEAK =
-SANITIZE_ADDRESS =
-
-# For the 'coccicheck' target
-SPATCH_INCLUDE_FLAGS = --all-includes
-SPATCH_FLAGS =
-SPATCH_TEST_FLAGS =
-
-# If *.o files are present, have "coccicheck" depend on them, with
-# COMPUTE_HEADER_DEPENDENCIES this will speed up the common-case of
-# only needing to re-generate coccicheck results for the users of a
-# given API if it's changed, and not all files in the project. If
-# COMPUTE_HEADER_DEPENDENCIES=no this will be unset too.
-SPATCH_USE_O_DEPENDENCIES = YesPlease
-
-# Set SPATCH_CONCAT_COCCI to concatenate the contrib/cocci/*.cocci
-# files into a single contrib/cocci/ALL.cocci before running
-# "coccicheck".
-#
-# Pros:
-#
-# - Speeds up a one-shot run of "make coccicheck", as we won't have to
-#   parse *.[ch] files N times for the N *.cocci rules
-#
-# Cons:
-#
-# - Will make incremental development of *.cocci slower, as
-#   e.g. changing strbuf.cocci will re-run all *.cocci.
-#
-# - Makes error and performance analysis harder, as rules will be
-#   applied from a monolithic ALL.cocci, rather than
-#   e.g. strbuf.cocci. To work around this either undefine this, or
-#   generate a specific patch, e.g. this will always use strbuf.cocci,
-#   not ALL.cocci:
-#
-#	make contrib/coccinelle/strbuf.cocci.patch
-SPATCH_CONCAT_COCCI = YesPlease
-
-# Rebuild 'coccicheck' if $(SPATCH), its flags etc. change
-TRACK_SPATCH_DEFINES =
-TRACK_SPATCH_DEFINES += $(SPATCH)
-TRACK_SPATCH_DEFINES += $(SPATCH_INCLUDE_FLAGS)
-TRACK_SPATCH_DEFINES += $(SPATCH_FLAGS)
-TRACK_SPATCH_DEFINES += $(SPATCH_TEST_FLAGS)
-GIT-SPATCH-DEFINES: FORCE
-	@FLAGS='$(TRACK_SPATCH_DEFINES)'; \
-	    if test x"$$FLAGS" != x"`cat GIT-SPATCH-DEFINES 2>/dev/null`" ; then \
-		echo >&2 "    * new spatch flags"; \
-		echo "$$FLAGS" >GIT-SPATCH-DEFINES; \
-            fi
-
-include config.mak.uname
--include config.mak.autogen
--include config.mak
-
-ifdef DEVELOPER
-include config.mak.dev
-endif
-
 GIT-VERSION-FILE: FORCE
 	@OLD=$$(cat $@ 2>/dev/null || :) && \
 	$(call version_gen,"$(shell pwd)",GIT-VERSION-FILE.in,$@) && \

From e30c081c6af4963418184dbcd5df37322032f9dc Mon Sep 17 00:00:00 2001
From: Patrick Steinhardt <ps@pks.im>
Date: Thu, 2 Oct 2025 09:29:28 +0200
Subject: [PATCH 06/13] Makefile: introduce infrastructure to build internal
 Rust library

Introduce infrastructure to build the internal Rust library. This
mirrors the infrastructure we have added to Meson in the preceding
commit. Developers can enable the infrastructure by passing the new
`WITH_RUST` build toggle.

Inspired-by: Ezekiel Newren <ezekielnewren@gmail.com>
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 .gitignore |  2 ++
 Makefile   | 37 +++++++++++++++++++++++++++++++++++++
 shared.mak |  1 +
 3 files changed, 40 insertions(+)

diff --git a/.gitignore b/.gitignore
index 1803023427af81..0833453cf6fec0 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,4 +1,6 @@
 /fuzz_corpora
+/target/
+/Cargo.lock
 /GIT-BUILD-DIR
 /GIT-BUILD-OPTIONS
 /GIT-CFLAGS
diff --git a/Makefile b/Makefile
index 7e52625d755061..31e79342e1d647 100644
--- a/Makefile
+++ b/Makefile
@@ -483,6 +483,14 @@ include shared.mak
 # Define LIBPCREDIR=/foo/bar if your PCRE header and library files are
 # in /foo/bar/include and /foo/bar/lib directories.
 #
+# == Optional Rust support ==
+#
+# Define WITH_RUST if you want to include features and subsystems written in
+# Rust into Git. For now, Rust is still an optional feature of the build
+# process. With Git 3.0 though, Rust will always be enabled.
+#
+# Building Rust code requires Cargo.
+#
 # == SHA-1 and SHA-256 defines ==
 #
 # === SHA-1 backend ===
@@ -683,6 +691,7 @@ OBJECTS =
 OTHER_PROGRAMS =
 PROGRAM_OBJS =
 PROGRAMS =
+RUST_SOURCES =
 EXCLUDED_PROGRAMS =
 SCRIPT_PERL =
 SCRIPT_PYTHON =
@@ -918,6 +927,11 @@ TEST_SHELL_PATH = $(SHELL_PATH)
 LIB_FILE = libgit.a
 XDIFF_LIB = xdiff/lib.a
 REFTABLE_LIB = reftable/libreftable.a
+ifdef DEBUG
+RUST_LIB = target/debug/libgitcore.a
+else
+RUST_LIB = target/release/libgitcore.a
+endif
 
 # xdiff and reftable libs may in turn depend on what is in libgit.a
 GITLIBS = common-main.o $(LIB_FILE) $(XDIFF_LIB) $(REFTABLE_LIB) $(LIB_FILE)
@@ -943,6 +957,15 @@ BASIC_LDFLAGS =
 ARFLAGS = rcs
 PTHREAD_CFLAGS =
 
+# Rust flags
+CARGO_ARGS =
+ifndef V
+CARGO_ARGS += --quiet
+endif
+ifndef DEBUG
+CARGO_ARGS += --release
+endif
+
 # For the 'sparse' target
 SPARSE_FLAGS ?= -std=gnu99 -D__STDC_NO_VLA__
 SP_EXTRA_FLAGS =
@@ -1475,6 +1498,8 @@ CLAR_TEST_OBJS += $(UNIT_TEST_DIR)/unit-test.o
 
 UNIT_TEST_OBJS += $(UNIT_TEST_DIR)/test-lib.o
 
+RUST_SOURCES += src/lib.rs
+
 GIT-VERSION-FILE: FORCE
 	@OLD=$$(cat $@ 2>/dev/null || :) && \
 	$(call version_gen,"$(shell pwd)",GIT-VERSION-FILE.in,$@) && \
@@ -1504,6 +1529,11 @@ endif
 ALL_CFLAGS = $(DEVELOPER_CFLAGS) $(CPPFLAGS) $(CFLAGS) $(CFLAGS_APPEND)
 ALL_LDFLAGS = $(LDFLAGS) $(LDFLAGS_APPEND)
 
+ifdef WITH_RUST
+BASIC_CFLAGS += -DWITH_RUST
+GITLIBS += $(RUST_LIB)
+endif
+
 ifdef SANITIZE
 SANITIZERS := $(foreach flag,$(subst $(comma),$(space),$(SANITIZE)),$(flag))
 BASIC_CFLAGS += -fsanitize=$(SANITIZE) -fno-sanitize-recover=$(SANITIZE)
@@ -2918,6 +2948,12 @@ scalar$X: scalar.o GIT-LDFLAGS $(GITLIBS)
 $(LIB_FILE): $(LIB_OBJS)
 	$(QUIET_AR)$(RM) $@ && $(AR) $(ARFLAGS) $@ $^
 
+$(RUST_LIB): Cargo.toml $(RUST_SOURCES)
+	$(QUIET_CARGO)cargo build $(CARGO_ARGS)
+
+.PHONY: rust
+rust: $(RUST_LIB)
+
 $(XDIFF_LIB): $(XDIFF_OBJS)
 	$(QUIET_AR)$(RM) $@ && $(AR) $(ARFLAGS) $@ $^
 
@@ -3768,6 +3804,7 @@ clean: profile-clean coverage-clean cocciclean
 	$(RM) $(FUZZ_PROGRAMS)
 	$(RM) $(SP_OBJ)
 	$(RM) $(HCC)
+	$(RM) -r Cargo.lock target/
 	$(RM) version-def.h
 	$(RM) -r $(dep_dirs) $(compdb_dir) compile_commands.json
 	$(RM) $(test_bindir_programs)
diff --git a/shared.mak b/shared.mak
index 5c7bc9478544c8..0e7492076ebc4f 100644
--- a/shared.mak
+++ b/shared.mak
@@ -56,6 +56,7 @@ ifndef V
 	QUIET_MKDIR_P_PARENT  = @echo '   ' MKDIR -p $(@D);
 
 ## Used in "Makefile"
+	QUIET_CARGO    = @echo '   ' CARGO $@;
 	QUIET_CC       = @echo '   ' CC $@;
 	QUIET_AR       = @echo '   ' AR $@;
 	QUIET_LINK     = @echo '   ' LINK $@;

From cb2badb4db67bcd02cc99a336c7b6bb0281980a1 Mon Sep 17 00:00:00 2001
From: Patrick Steinhardt <ps@pks.im>
Date: Thu, 2 Oct 2025 09:29:29 +0200
Subject: [PATCH 07/13] help: report on whether or not Rust is enabled

We're about to introduce support for Rust into the core of Git, where
some (trivial) subsystems are converted to Rust. These subsystems will
also retain a C implementation though as Rust is not yet mandatory.
Consequently, it now becomes possible for a Git version to have bugs
that are specific to whether or not it is built with Rust support
overall.

Expose information about whether or not Git was built with Rust via our
build info. This means that both `git version --build-options`, but also
`git bugreport` will now expose that bit of information. Hopefully, this
should make it easier for us to discover any Rust-specific issues.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 help.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/help.c b/help.c
index bb20498cfd0f15..5854dd4a7e468b 100644
--- a/help.c
+++ b/help.c
@@ -791,6 +791,12 @@ void get_version_info(struct strbuf *buf, int show_build_options)
 		strbuf_addf(buf, "shell-path: %s\n", SHELL_PATH);
 		/* NEEDSWORK: also save and output GIT-BUILD_OPTIONS? */
 
+#if defined WITH_RUST
+		strbuf_addstr(buf, "rust: enabled\n");
+#else
+		strbuf_addstr(buf, "rust: disabled\n");
+#endif
+
 		if (fsmonitor_ipc__is_supported())
 			strbuf_addstr(buf, "feature: fsmonitor--daemon\n");
 #if defined LIBCURL_VERSION

From f366bfe16b350240c70c487d180c76ddcb8a1b2d Mon Sep 17 00:00:00 2001
From: Patrick Steinhardt <ps@pks.im>
Date: Thu, 2 Oct 2025 09:29:30 +0200
Subject: [PATCH 08/13] varint: use explicit width for integers

The varint subsystem currently uses implicit widths for integers. On the
one hand we use `uintmax_t` for the actual value. On the other hand, we
use `int` for the length of the encoded varint.

Both of these have known maximum values, as we only support at most 16
bytes when encoding varints. Thus, we know that we won't ever exceed
`uint64_t` for the actual value and `uint8_t` for the prefix length.

Refactor the code to use explicit widths. Besides making the logic
platform-independent, it also makes our life a bit easier in the next
commit, where we reimplement "varint.c" in Rust.

Suggested-by: Ezekiel Newren <ezekielnewren@gmail.com>
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 dir.c        | 18 ++++++++++--------
 read-cache.c |  6 ++++--
 varint.c     |  6 +++---
 varint.h     |  4 ++--
 4 files changed, 19 insertions(+), 15 deletions(-)

diff --git a/dir.c b/dir.c
index 71108ac79b78b8..0a67a99cb3dd3f 100644
--- a/dir.c
+++ b/dir.c
@@ -3579,7 +3579,8 @@ static void write_one_dir(struct untracked_cache_dir *untracked,
 	struct stat_data stat_data;
 	struct strbuf *out = &wd->out;
 	unsigned char intbuf[16];
-	unsigned int intlen, value;
+	unsigned int value;
+	uint8_t intlen;
 	int i = wd->index++;
 
 	/*
@@ -3632,7 +3633,7 @@ void write_untracked_extension(struct strbuf *out, struct untracked_cache *untra
 	struct ondisk_untracked_cache *ouc;
 	struct write_data wd;
 	unsigned char varbuf[16];
-	int varint_len;
+	uint8_t varint_len;
 	const unsigned hashsz = the_hash_algo->rawsz;
 
 	CALLOC_ARRAY(ouc, 1);
@@ -3738,7 +3739,7 @@ static int read_one_dir(struct untracked_cache_dir **untracked_,
 	struct untracked_cache_dir ud, *untracked;
 	const unsigned char *data = rd->data, *end = rd->end;
 	const unsigned char *eos;
-	unsigned int value;
+	uint64_t value;
 	int i;
 
 	memset(&ud, 0, sizeof(ud));
@@ -3830,7 +3831,8 @@ struct untracked_cache *read_untracked_extension(const void *data, unsigned long
 	struct read_data rd;
 	const unsigned char *next = data, *end = (const unsigned char *)data + sz;
 	const char *ident;
-	int ident_len;
+	uint64_t ident_len;
+	uint64_t varint_len;
 	ssize_t len;
 	const char *exclude_per_dir;
 	const unsigned hashsz = the_hash_algo->rawsz;
@@ -3867,8 +3869,8 @@ struct untracked_cache *read_untracked_extension(const void *data, unsigned long
 	if (next >= end)
 		goto done2;
 
-	len = decode_varint(&next);
-	if (next > end || len == 0)
+	varint_len = decode_varint(&next);
+	if (next > end || varint_len == 0)
 		goto done2;
 
 	rd.valid      = ewah_new();
@@ -3877,9 +3879,9 @@ struct untracked_cache *read_untracked_extension(const void *data, unsigned long
 	rd.data	      = next;
 	rd.end	      = end;
 	rd.index      = 0;
-	ALLOC_ARRAY(rd.ucd, len);
+	ALLOC_ARRAY(rd.ucd, varint_len);
 
-	if (read_one_dir(&uc->root, &rd) || rd.index != len)
+	if (read_one_dir(&uc->root, &rd) || rd.index != varint_len)
 		goto done;
 
 	next = rd.data;
diff --git a/read-cache.c b/read-cache.c
index 06ad74db2286ae..41b44148b1e04f 100644
--- a/read-cache.c
+++ b/read-cache.c
@@ -1807,7 +1807,7 @@ static struct cache_entry *create_from_disk(struct mem_pool *ce_mem_pool,
 
 	if (expand_name_field) {
 		const unsigned char *cp = (const unsigned char *)name;
-		size_t strip_len, previous_len;
+		uint64_t strip_len, previous_len;
 
 		/* If we're at the beginning of a block, ignore the previous name */
 		strip_len = decode_varint(&cp);
@@ -2655,8 +2655,10 @@ static int ce_write_entry(struct hashfile *f, struct cache_entry *ce,
 		hashwrite(f, ce->name, len);
 		hashwrite(f, padding, align_padding_size(size, len));
 	} else {
-		int common, to_remove, prefix_size;
+		int common, to_remove;
+		uint8_t prefix_size;
 		unsigned char to_remove_vi[16];
+
 		for (common = 0;
 		     (common < previous_name->len &&
 		      ce->name[common] &&
diff --git a/varint.c b/varint.c
index 409c4977a1e3a3..03cd54416b6a46 100644
--- a/varint.c
+++ b/varint.c
@@ -1,11 +1,11 @@
 #include "git-compat-util.h"
 #include "varint.h"
 
-uintmax_t decode_varint(const unsigned char **bufp)
+uint64_t decode_varint(const unsigned char **bufp)
 {
 	const unsigned char *buf = *bufp;
 	unsigned char c = *buf++;
-	uintmax_t val = c & 127;
+	uint64_t val = c & 127;
 	while (c & 128) {
 		val += 1;
 		if (!val || MSB(val, 7))
@@ -17,7 +17,7 @@ uintmax_t decode_varint(const unsigned char **bufp)
 	return val;
 }
 
-int encode_varint(uintmax_t value, unsigned char *buf)
+uint8_t encode_varint(uint64_t value, unsigned char *buf)
 {
 	unsigned char varint[16];
 	unsigned pos = sizeof(varint) - 1;
diff --git a/varint.h b/varint.h
index f78bb0ca528dcd..eb401935bd24c9 100644
--- a/varint.h
+++ b/varint.h
@@ -1,7 +1,7 @@
 #ifndef VARINT_H
 #define VARINT_H
 
-int encode_varint(uintmax_t, unsigned char *);
-uintmax_t decode_varint(const unsigned char **);
+uint8_t encode_varint(uint64_t, unsigned char *);
+uint64_t decode_varint(const unsigned char **);
 
 #endif /* VARINT_H */

From 8832e728d362992a38eef89613b44d24f18e6c2a Mon Sep 17 00:00:00 2001
From: Patrick Steinhardt <ps@pks.im>
Date: Thu, 2 Oct 2025 09:29:31 +0200
Subject: [PATCH 09/13] varint: reimplement as test balloon for Rust

Implement a trivial test balloon for our Rust build infrastructure by
reimplementing the "varint.c" subsystem in Rust. This subsystem is
chosen because it is trivial to convert and because it doesn't have any
dependencies to other components of Git.

If support for Rust is enabled, we stop compiling "varint.c" and instead
compile and use "src/varint.rs".

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 Makefile        |  3 ++
 meson.build     |  5 ++-
 src/lib.rs      |  1 +
 src/meson.build |  1 +
 src/varint.rs   | 92 +++++++++++++++++++++++++++++++++++++++++++++++++
 5 files changed, 101 insertions(+), 1 deletion(-)
 create mode 100644 src/varint.rs

diff --git a/Makefile b/Makefile
index 31e79342e1d647..2a7fc5cb1f30fa 100644
--- a/Makefile
+++ b/Makefile
@@ -1307,7 +1307,9 @@ LIB_OBJS += urlmatch.o
 LIB_OBJS += usage.o
 LIB_OBJS += userdiff.o
 LIB_OBJS += utf8.o
+ifndef WITH_RUST
 LIB_OBJS += varint.o
+endif
 LIB_OBJS += version.o
 LIB_OBJS += versioncmp.o
 LIB_OBJS += walker.o
@@ -1499,6 +1501,7 @@ CLAR_TEST_OBJS += $(UNIT_TEST_DIR)/unit-test.o
 UNIT_TEST_OBJS += $(UNIT_TEST_DIR)/test-lib.o
 
 RUST_SOURCES += src/lib.rs
+RUST_SOURCES += src/varint.rs
 
 GIT-VERSION-FILE: FORCE
 	@OLD=$$(cat $@ 2>/dev/null || :) && \
diff --git a/meson.build b/meson.build
index 234a9e9d6fd461..37dfa286017d22 100644
--- a/meson.build
+++ b/meson.build
@@ -522,7 +522,6 @@ libgit_sources = [
   'usage.c',
   'userdiff.c',
   'utf8.c',
-  'varint.c',
   'version.c',
   'versioncmp.c',
   'walker.c',
@@ -1707,6 +1706,10 @@ rust_option = get_option('rust').disable_auto_if(not cargo.found())
 if rust_option.allowed()
   subdir('src')
   libgit_c_args += '-DWITH_RUST'
+else
+  libgit_sources += [
+    'varint.c',
+  ]
 endif
 
 libgit = declare_dependency(
diff --git a/src/lib.rs b/src/lib.rs
index e69de29bb2d1d6..9da70d8b57d5f6 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -0,0 +1 @@
+pub mod varint;
diff --git a/src/meson.build b/src/meson.build
index c8d874b2106176..25b9ad5a1479c0 100644
--- a/src/meson.build
+++ b/src/meson.build
@@ -1,5 +1,6 @@
 libgit_rs_sources = [
   'lib.rs',
+  'varint.rs',
 ]
 
 # Unfortunately we must use a wrapper command to move the output file into the
diff --git a/src/varint.rs b/src/varint.rs
new file mode 100644
index 00000000000000..6e610bdd8e0794
--- /dev/null
+++ b/src/varint.rs
@@ -0,0 +1,92 @@
+#[no_mangle]
+pub unsafe extern "C" fn decode_varint(bufp: *mut *const u8) -> u64 {
+    let mut buf = *bufp;
+    let mut c = *buf;
+    let mut val = u64::from(c & 127);
+
+    buf = buf.add(1);
+
+    while (c & 128) != 0 {
+        val = val.wrapping_add(1);
+        if val == 0 || val.leading_zeros() < 7 {
+            return 0; // overflow
+        }
+
+        c = *buf;
+        buf = buf.add(1);
+
+        val = (val << 7) + u64::from(c & 127);
+    }
+
+    *bufp = buf;
+    val
+}
+
+#[no_mangle]
+pub unsafe extern "C" fn encode_varint(value: u64, buf: *mut u8) -> u8 {
+    let mut varint: [u8; 16] = [0; 16];
+    let mut pos = varint.len() - 1;
+
+    varint[pos] = (value & 127) as u8;
+
+    let mut value = value >> 7;
+    while value != 0 {
+        pos -= 1;
+        value -= 1;
+        varint[pos] = 128 | (value & 127) as u8;
+        value >>= 7;
+    }
+
+    if !buf.is_null() {
+        std::ptr::copy_nonoverlapping(varint.as_ptr().add(pos), buf, varint.len() - pos);
+    }
+
+    (varint.len() - pos) as u8
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_decode_varint() {
+        unsafe {
+            assert_eq!(decode_varint(&mut [0x00].as_slice().as_ptr()), 0);
+            assert_eq!(decode_varint(&mut [0x01].as_slice().as_ptr()), 1);
+            assert_eq!(decode_varint(&mut [0x7f].as_slice().as_ptr()), 127);
+            assert_eq!(decode_varint(&mut [0x80, 0x00].as_slice().as_ptr()), 128);
+            assert_eq!(decode_varint(&mut [0x80, 0x01].as_slice().as_ptr()), 129);
+            assert_eq!(decode_varint(&mut [0x80, 0x7f].as_slice().as_ptr()), 255);
+
+            // Overflows are expected to return 0.
+            assert_eq!(decode_varint(&mut [0x88; 16].as_slice().as_ptr()), 0);
+        }
+    }
+
+    #[test]
+    fn test_encode_varint() {
+        unsafe {
+            let mut varint: [u8; 16] = [0; 16];
+
+            assert_eq!(encode_varint(0, std::ptr::null_mut()), 1);
+
+            assert_eq!(encode_varint(0, varint.as_mut_slice().as_mut_ptr()), 1);
+            assert_eq!(varint, [0; 16]);
+
+            assert_eq!(encode_varint(10, varint.as_mut_slice().as_mut_ptr()), 1);
+            assert_eq!(varint, [10, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]);
+
+            assert_eq!(encode_varint(127, varint.as_mut_slice().as_mut_ptr()), 1);
+            assert_eq!(varint, [127, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]);
+
+            assert_eq!(encode_varint(128, varint.as_mut_slice().as_mut_ptr()), 2);
+            assert_eq!(varint, [128, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]);
+
+            assert_eq!(encode_varint(129, varint.as_mut_slice().as_mut_ptr()), 2);
+            assert_eq!(varint, [128, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]);
+
+            assert_eq!(encode_varint(255, varint.as_mut_slice().as_mut_ptr()), 2);
+            assert_eq!(varint, [128, 127, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]);
+        }
+    }
+}

From 8f5daaff927e868b0460dda40cdb0923b8a6ef35 Mon Sep 17 00:00:00 2001
From: Patrick Steinhardt <ps@pks.im>
Date: Thu, 2 Oct 2025 09:29:32 +0200
Subject: [PATCH 10/13] BreakingChanges: announce Rust becoming mandatory

Over the last couple of years the appetite for bringing Rust into the
codebase has grown significantly across the developer base. Introducing
Rust is a major change though and has ramifications for the whole
ecosystem:

  - Some platforms have a Rust toolchain available, but have not yet
    integrated it into their build infrastructure.

  - Some platforms don't have any support for Rust at all.

  - Some platforms may have to figure out how to fit Rust into their
    bootstrapping sequence.

Due to this, and given that Git is a critical piece of infrastructure
for the whole industry, we cannot just introduce such a heavyweight
dependency without doing our due diligence.

Instead, preceding commits have introduced a test balloon into our build
infrastructure that convert one tiny subsystem to use Rust. For now,
using Rust to build that subsystem is entirely optional -- if no Rust
support is available, we continue to use the C implementation. This test
balloon has the intention to give distributions time and let them ease
into our adoption of Rust.

Having multiple implementations of the same subsystem is not sustainable
though, and the plan is to eventually be able to use Rust freely all
across our codebase. As such, there is the intent to make Rust become a
mandatory part of our build process.

Add an announcement to our breaking changes that Rust will become
mandatory in Git 3.0. A (very careful and non-binding) estimate might be
that this major release might be released in the second half of next
year, which should give distributors enough time to prepare for the
change.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 Documentation/BreakingChanges.adoc | 45 ++++++++++++++++++++++++++++++
 1 file changed, 45 insertions(+)

diff --git a/Documentation/BreakingChanges.adoc b/Documentation/BreakingChanges.adoc
index f8d2eba061c82a..c21f9021343fea 100644
--- a/Documentation/BreakingChanges.adoc
+++ b/Documentation/BreakingChanges.adoc
@@ -165,6 +165,51 @@ A prerequisite for this change is that the ecosystem is ready to support the
 "reftable" format. Most importantly, alternative implementations of Git like
 JGit, libgit2 and Gitoxide need to support it.
 
+* Git will require Rust as a mandatory part of the build process. While Git
+  already started to adopt Rust in Git 2.49, all parts written in Rust are
+  optional for the time being. This includes:
++
+  ** The Rust wrapper around libgit.a that is part of "contrib/" and which has
+     been introduced in Git 2.49.
+  ** Subsystems that have an alternative implementation in Rust to test
+     interoperability between our C and Rust codebase.
+  ** Newly written features that are not mission critical for a fully functional
+     Git client.
++
+These changes are meant as test balloons to allow distributors of Git to prepare
+for Rust becoming a mandatory part of the build process. There will be multiple
+milestones for the introduction of Rust:
++
+--
+1. Initially, with Git 2.52, support for Rust will be auto-detected by Meson and
+   disabled in our Makefile so that the project can sort out the initial
+   infrastructure.
+2. In Git 2.53, both build systems will default-enable support for Rust.
+   Consequently, builds will break by default if Rust is not available on the
+   build host. The use of Rust can still be explicitly disabled via build
+   flags.
+3. In Git 3.0, the build options will be removed and support for Rust is
+   mandatory.
+--
++
+You can explicitly ask both Meson and our Makefile-based system to enable Rust
+by saying `meson configure -Drust=enabled` and `make WITH_RUST=YesPlease`,
+respectively.
++
+The Git project will declare the last version before Git 3.0 to be a long-term
+support release. This long-term release will receive important bug fixes for at
+least four release cycles and security fixes for six release cycles. The Git
+project will hand over maintainership of the long-term release to distributors
+in case they need to extend the life of that long-term release even further.
+Details of how this long-term release will be handed over to the community will
+be discussed once the Git project decides to stop officially supporting it.
++
+We will evaluate the impact on downstream distributions before making Rust
+mandatory in Git 3.0. If we see that the impact on downstream distributions
+would be significant, we may decide to defer this change to a subsequent minor
+release. This evaluation will also take into account our own experience with
+how painful it is to keep Rust an optional component.
+
 === Removals
 
 * Support for grafting commits has long been superseded by git-replace(1).

From 6ab3977200fc6f69c1a01c0dbefabbbed6b45fb0 Mon Sep 17 00:00:00 2001
From: Patrick Steinhardt <ps@pks.im>
Date: Thu, 2 Oct 2025 09:29:33 +0200
Subject: [PATCH 11/13] ci: convert "pedantic" job into full build with
 breaking changes

The "pedantic" CI job is building on Fedora with `DEVOPTS=pedantic`.
This build flag doesn't do anything anymore starting with 6a8cbc41ba
(developer: enable pedantic by default, 2021-09-03), where we have
flipped the default so that developers have to opt-out of pedantic
builds via the "no-pedantic" option. As such, all this job really does
is to do a normal build on Fedora, which isn't all that interesting.

Convert that job into a full build-and-test job that uses Meson with
breaking changes enabled. This plugs two gaps:

  - We now test on another distro that we didn't run tests on
    beforehand.

  - We verify that breaking changes work as expected with Meson.

Furthermore, in a subsequent commit we'll modify both jobs that use
breaking changes to also enable Rust. By converting the Fedora job to
use Meson, we ensure that we test our Rust build infrastructure for both
build systems.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 .github/workflows/main.yml |  4 ++--
 .gitlab-ci.yml             |  4 ++--
 ci/install-dependencies.sh |  6 +++++-
 ci/run-build-and-tests.sh  | 29 ++++++++---------------------
 4 files changed, 17 insertions(+), 26 deletions(-)

diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index d122e79415a13e..393ea4d1ccf784 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -379,6 +379,8 @@ jobs:
         - jobname: linux-breaking-changes
           cc: gcc
           image: ubuntu:rolling
+        - jobname: fedora-breaking-changes-meson
+          image: fedora:latest
         - jobname: linux-leaks
           image: ubuntu:rolling
           cc: gcc
@@ -396,8 +398,6 @@ jobs:
         # Supported until 2025-04-02.
         - jobname: linux32
           image: i386/ubuntu:focal
-        - jobname: pedantic
-          image: fedora:latest
         # A RHEL 8 compatible distro.  Supported until 2029-05-31.
         - jobname: almalinux-8
           image: almalinux:8
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index af10ebb59a3ada..4248506909959b 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -45,6 +45,8 @@ test:linux:
       - jobname: linux-breaking-changes
         image: ubuntu:20.04
         CC: gcc
+      - jobname: fedora-breaking-changes-meson
+        image: fedora:latest
       - jobname: linux-TEST-vars
         image: ubuntu:20.04
         CC: gcc
@@ -58,8 +60,6 @@ test:linux:
       - jobname: linux-asan-ubsan
         image: ubuntu:rolling
         CC: clang
-      - jobname: pedantic
-        image: fedora:latest
       - jobname: linux-musl-meson
         image: alpine:latest
       - jobname: linux32
diff --git a/ci/install-dependencies.sh b/ci/install-dependencies.sh
index d061a4729339e0..35bd05b85b9085 100755
--- a/ci/install-dependencies.sh
+++ b/ci/install-dependencies.sh
@@ -30,8 +30,12 @@ alpine-*)
 		bash cvs gnupg perl-cgi perl-dbd-sqlite perl-io-tty >/dev/null
 	;;
 fedora-*|almalinux-*)
+	case "$jobname" in
+	*-meson)
+		MESON_DEPS="meson ninja";;
+	esac
 	dnf -yq update >/dev/null &&
-	dnf -yq install shadow-utils sudo make gcc findutils diffutils perl python3 gawk gettext zlib-devel expat-devel openssl-devel curl-devel pcre2-devel >/dev/null
+	dnf -yq install shadow-utils sudo make pkg-config gcc findutils diffutils perl python3 gawk gettext zlib-devel expat-devel openssl-devel curl-devel pcre2-devel $MESON_DEPS >/dev/null
 	;;
 ubuntu-*|i386/ubuntu-*|debian-*)
 	# Required so that apt doesn't wait for user input on certain packages.
diff --git a/ci/run-build-and-tests.sh b/ci/run-build-and-tests.sh
index 01823fd0f140bb..3680446649e694 100755
--- a/ci/run-build-and-tests.sh
+++ b/ci/run-build-and-tests.sh
@@ -5,12 +5,11 @@
 
 . ${0%/*}/lib.sh
 
-run_tests=t
-
 case "$jobname" in
-linux-breaking-changes)
+fedora-breaking-changes-musl|linux-breaking-changes)
 	export GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME=main
 	export WITH_BREAKING_CHANGES=YesPlease
+	MESONFLAGS="$MESONFLAGS -Dbreaking_changes=true"
 	;;
 linux-TEST-vars)
 	export OPENSSL_SHA1_UNSAFE=YesPlease
@@ -36,12 +35,6 @@ linux-sha256)
 linux-reftable|linux-reftable-leaks|osx-reftable)
 	export GIT_TEST_DEFAULT_REF_FORMAT=reftable
 	;;
-pedantic)
-	# Don't run the tests; we only care about whether Git can be
-	# built.
-	export DEVOPTS=pedantic
-	run_tests=
-	;;
 esac
 
 case "$jobname" in
@@ -54,21 +47,15 @@ case "$jobname" in
 		-Dtest_output_directory="${TEST_OUTPUT_DIRECTORY:-$(pwd)/t}" \
 		$MESONFLAGS
 	group "Build" meson compile -C build --
-	if test -n "$run_tests"
-	then
-		group "Run tests" meson test -C build --print-errorlogs --test-args="$GIT_TEST_OPTS" || (
-			./t/aggregate-results.sh "${TEST_OUTPUT_DIRECTORY:-t}/test-results"
-			handle_failed_tests
-		)
-	fi
+	group "Run tests" meson test -C build --print-errorlogs --test-args="$GIT_TEST_OPTS" || (
+		./t/aggregate-results.sh "${TEST_OUTPUT_DIRECTORY:-t}/test-results"
+		handle_failed_tests
+	)
 	;;
 *)
 	group Build make
-	if test -n "$run_tests"
-	then
-		group "Run tests" make test ||
-		handle_failed_tests
-	fi
+	group "Run tests" make test ||
+	handle_failed_tests
 	;;
 esac
 

From e425c40aa00d2ae6b1bbc33cfa9fecd30a0a8ec6 Mon Sep 17 00:00:00 2001
From: Patrick Steinhardt <ps@pks.im>
Date: Thu, 2 Oct 2025 09:29:34 +0200
Subject: [PATCH 12/13] ci: enable Rust for breaking-changes jobs

Enable Rust for our breaking-changes jobs so that we can verify that the
build infrastructure and the converted Rust subsystems work as expected.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 ci/install-dependencies.sh | 4 ++--
 ci/run-build-and-tests.sh  | 2 ++
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/ci/install-dependencies.sh b/ci/install-dependencies.sh
index 35bd05b85b9085..0d3aa496fc3a24 100755
--- a/ci/install-dependencies.sh
+++ b/ci/install-dependencies.sh
@@ -35,7 +35,7 @@ fedora-*|almalinux-*)
 		MESON_DEPS="meson ninja";;
 	esac
 	dnf -yq update >/dev/null &&
-	dnf -yq install shadow-utils sudo make pkg-config gcc findutils diffutils perl python3 gawk gettext zlib-devel expat-devel openssl-devel curl-devel pcre2-devel $MESON_DEPS >/dev/null
+	dnf -yq install shadow-utils sudo make pkg-config gcc findutils diffutils perl python3 gawk gettext zlib-devel expat-devel openssl-devel curl-devel pcre2-devel $MESON_DEPS cargo >/dev/null
 	;;
 ubuntu-*|i386/ubuntu-*|debian-*)
 	# Required so that apt doesn't wait for user input on certain packages.
@@ -62,7 +62,7 @@ ubuntu-*|i386/ubuntu-*|debian-*)
 		make libssl-dev libcurl4-openssl-dev libexpat-dev wget sudo default-jre \
 		tcl tk gettext zlib1g-dev perl-modules liberror-perl libauthen-sasl-perl \
 		libemail-valid-perl libio-pty-perl libio-socket-ssl-perl libnet-smtp-ssl-perl libdbd-sqlite3-perl libcgi-pm-perl \
-		libsecret-1-dev libpcre2-dev meson ninja-build pkg-config \
+		libsecret-1-dev libpcre2-dev meson ninja-build pkg-config cargo \
 		${CC_PACKAGE:-${CC:-gcc}} $PYTHON_PACKAGE
 
 	case "$distro" in
diff --git a/ci/run-build-and-tests.sh b/ci/run-build-and-tests.sh
index 3680446649e694..c718bd101aa8bb 100755
--- a/ci/run-build-and-tests.sh
+++ b/ci/run-build-and-tests.sh
@@ -9,7 +9,9 @@ case "$jobname" in
 fedora-breaking-changes-musl|linux-breaking-changes)
 	export GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME=main
 	export WITH_BREAKING_CHANGES=YesPlease
+	export WITH_RUST=YesPlease
 	MESONFLAGS="$MESONFLAGS -Dbreaking_changes=true"
+	MESONFLAGS="$MESONFLAGS -Drust=enabled"
 	;;
 linux-TEST-vars)
 	export OPENSSL_SHA1_UNSAFE=YesPlease

From 60f3f52f17cceefa5299709b189ce6fe2d181e7b Mon Sep 17 00:00:00 2001
From: Junio C Hamano <gitster@pobox.com>
Date: Wed, 8 Oct 2025 09:31:33 -0700
Subject: [PATCH 13/13] The sixteenth batch

Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 Documentation/RelNotes/2.52.0.adoc | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/Documentation/RelNotes/2.52.0.adoc b/Documentation/RelNotes/2.52.0.adoc
index ee7ea2e43379e7..7fb1a3ce18a87d 100644
--- a/Documentation/RelNotes/2.52.0.adoc
+++ b/Documentation/RelNotes/2.52.0.adoc
@@ -113,6 +113,9 @@ Performance, Internal Implementation, Development Support etc.
    documentation, similar to "make doc".
    (merge ff4ec8ded0 ps/meson-build-docs later to maint).
 
+ * Dip our toes a bit to (optionally) use Rust implemented helper
+   called from our C code.
+
 
 Fixes since v2.51
 -----------------
@@ -289,6 +292,12 @@ including security updates, are included in this release.
    checking has been updated to use the existing helper function.
    (merge ecc5749578 js/curl-off-t-fixes later to maint).
 
+ * "git reflog write" did not honor the configured user.name/email
+   which has been corrected.
+
+ * Handling of an empty subdirectory of .git/refs/ in the ref-files
+   backend has been corrected.
+
  * Other code cleanup, docfix, build fix, etc.
    (merge 823d537fa7 kh/doc-git-log-markup-fix later to maint).
    (merge cf7efa4f33 rj/t6137-cygwin-fix later to maint).
@@ -315,3 +324,4 @@ including security updates, are included in this release.
    (merge fafc9b08b8 ag/doc-sendmail-gmail-example-update later to maint).
    (merge a66fc22bf9 rs/get-oid-with-flags-cleanup later to maint).
    (merge e1d062e8ba ps/odb-clean-stale-wrappers later to maint).
+   (merge fdd21ba116 mh/doc-credential-url-prefix later to maint).