diff --git a/Documentation/RelNotes/2.51.0.adoc b/Documentation/RelNotes/2.51.0.adoc
index f8adc2c5cf3b61..a73ea3e8086ce4 100644
--- a/Documentation/RelNotes/2.51.0.adoc
+++ b/Documentation/RelNotes/2.51.0.adoc
@@ -97,8 +97,8 @@ Performance, Internal Implementation, Development Support etc.
  * "git push" and "git fetch" are taught to update refs in batches to
    gain performance.
 
- * Some code paths in the "git prune" used to ignore passed in
-   repository object and used the_repository singleton instance
+ * Some code paths in "git prune" used to ignore the passed-in
+   repository object and used the `the_repository` singleton instance
    instead, which has been corrected.
 
  * Update ".clang-format" and ".editorconfig" to match our style guide
@@ -139,7 +139,7 @@ Performance, Internal Implementation, Development Support etc.
  * Redefine where the multi-pack-index sits in the object subsystem,
    which recently was restructured to allow multiple backends that
    support a single object source that belongs to one repository.  A
-   midx does span mulitple "object sources".
+   MIDX does span multiple "object sources".
 
  * Reduce implicit assumption and dependence on the_repository in the
    object-file subsystem.
@@ -292,11 +292,15 @@ including security updates, are included in this release.
    and also they learn to honor the -U<n> command-line option.
    (merge 2b3ae04011 lm/add-p-context later to maint).
 
- * The case where a new submodule takes a path where used to be a
-   completely different subproject is now dealt a bit better than
+ * The case where a new submodule takes a path where there used to be a
+   completely different subproject is now dealt with a bit better than
    before.
    (merge 5ed8c5b465 kj/renamed-submodule later to maint).
 
+ * The deflate codepath in "git archive --format=zip" had a
+   longstanding bug coming from misuse of zlib API, which has been
+   corrected.
+
  * Other code cleanup, docfix, build fix, etc.
    (merge b257adb571 lo/my-first-ow-doc-update later to maint).
    (merge 8b34b6a220 ly/sequencer-update-squash-is-fixup-only later to maint).
@@ -333,3 +337,5 @@ including security updates, are included in this release.
    (merge 3bdd897413 ms/meson-with-ancient-git-wo-ls-files-dedup later to maint).
    (merge cca758d324 kh/doc-fast-import-historical later to maint).
    (merge 9b0781196a jc/test-hashmap-is-still-here later to maint).
+   (merge 1bad05bacc jk/revert-squelch-compiler-warning later to maint).
+   (merge 3a7e783d9c dl/squelch-maybe-uninitialized later to maint).
diff --git a/GIT-VERSION-GEN b/GIT-VERSION-GEN
index 63463c87739aa0..e7e91190ae2d0d 100755
--- a/GIT-VERSION-GEN
+++ b/GIT-VERSION-GEN
@@ -1,6 +1,6 @@
 #!/bin/sh
 
-DEF_VER=v2.50.GIT
+DEF_VER=v2.51.0-rc1
 
 LF='
 '
diff --git a/archive-zip.c b/archive-zip.c
index dbd90d9c3d4b32..bea5bdd43dc43e 100644
--- a/archive-zip.c
+++ b/archive-zip.c
@@ -492,14 +492,22 @@ static int write_zip_entry(struct archiver_args *args,
 
 		zstream.next_in = buf;
 		zstream.avail_in = 0;
-		result = git_deflate(&zstream, Z_FINISH);
-		if (result != Z_STREAM_END)
-			die("deflate error (%d)", result);
+
+		do {
+			result = git_deflate(&zstream, Z_FINISH);
+			if (result != Z_OK && result != Z_STREAM_END)
+				die("deflate error (%d)", result);
+
+			out_len = zstream.next_out - compressed;
+			if (out_len > 0) {
+				write_or_die(1, compressed, out_len);
+				compressed_size += out_len;
+				zstream.next_out = compressed;
+				zstream.avail_out = sizeof(compressed);
+			}
+		} while (result != Z_STREAM_END);
 
 		git_deflate_end(&zstream);
-		out_len = zstream.next_out - compressed;
-		write_or_die(1, compressed, out_len);
-		compressed_size += out_len;
 		zip_offset += compressed_size;
 
 		write_zip_data_desc(size, compressed_size, crc);
diff --git a/builtin/remote.c b/builtin/remote.c
index 43a122740af300..8961ae6a8973c7 100644
--- a/builtin/remote.c
+++ b/builtin/remote.c
@@ -1474,10 +1474,13 @@ static int set_head(int argc, const char **argv, const char *prefix,
 	};
 	argc = parse_options(argc, argv, prefix, options,
 			     builtin_remote_sethead_usage, 0);
-	if (argc) {
-		strbuf_addf(&b_head, "refs/remotes/%s/HEAD", argv[0]);
-		remote = remote_get(argv[0]);
-	}
+
+	/* All modes require at least a remote name. */
+	if (!argc)
+		usage_with_options(builtin_remote_sethead_usage, options);
+
+	strbuf_addf(&b_head, "refs/remotes/%s/HEAD", argv[0]);
+	remote = remote_get(argv[0]);
 
 	if (!opt_a && !opt_d && argc == 2) {
 		head_name = xstrdup(argv[1]);
diff --git a/builtin/revert.c b/builtin/revert.c
index e07c2217fe846b..c3f92b585df8c9 100644
--- a/builtin/revert.c
+++ b/builtin/revert.c
@@ -111,7 +111,7 @@ static int run_sequencer(int argc, const char **argv, const char *prefix,
 	const char * const * usage_str = revert_or_cherry_pick_usage(opts);
 	const char *me = action_name(opts);
 	const char *cleanup_arg = NULL;
-	const char sentinel_value;
+	const char sentinel_value = 0; /* value not important */
 	const char *strategy = &sentinel_value;
 	const char *gpg_sign = &sentinel_value;
 	enum empty_action empty_opt = EMPTY_COMMIT_UNSPECIFIED;
diff --git a/t/unit-tests/clar/clar.c b/t/unit-tests/clar/clar.c
index d54e4553674908..03a3aa8e873bfc 100644
--- a/t/unit-tests/clar/clar.c
+++ b/t/unit-tests/clar/clar.c
@@ -350,7 +350,7 @@ static void
 clar_run_suite(const struct clar_suite *suite, const char *filter)
 {
 	const struct clar_func *test = suite->tests;
-	size_t i, matchlen;
+	size_t i, matchlen = 0;
 	struct clar_report *report;
 	int exact = 0;