During interactive rebase, using 'drop' on a merge commit lead to
an error, which was incorrect.

* js/rebase-i-allow-drop-on-a-merge:
  rebase -i: permit 'drop' of a merge commit

"git refs migrate" to migrate the reflog entries from a refs
backend to another had a handful of bugs squashed.

* ps/reflog-migrate-fixes:
  refs: fix invalid old object IDs when migrating reflogs
  refs: stop unsetting REF_HAVE_OLD for log-only updates
  refs/files: detect race when generating reflog entry for HEAD
  refs: fix identity for migrated reflogs
  ident: fix type of string length parameter
  builtin/reflog: implement subcommand to write new entries
  refs: export `ref_transaction_update_reflog()`
  builtin/reflog: improve grouping of subcommands
  Documentation/git-reflog: convert to use synopsis type

"git push" had a code path that led to BUG() but it should have
been a die(), as it is a response to a usual but invalid end-user
action to attempt pushing an object that does not exist.
cf. <xmqqo6spiyqp.fsf@gitster.g>

* dl/push-missing-object-error:
  remote.c: convert if-else ladder to switch
  remote.c: remove BUG in show_push_unqualified_ref_name_error()
  t5516: remove surrounding empty lines in test bodies

Various bugs about rename handling in "ort" merge strategy have
been fixed.

* en/ort-rename-fixes:
  merge-ort: fix directory rename on top of source of other rename/delete
  merge-ort: fix incorrect file handling
  merge-ort: clarify the interning of strings in opt->priv->path
  t6423: fix missed staging of file in testcases 12i,12j,12k
  t6423: document two bugs with rename-to-self testcases
  merge-ort: drop unnecessary temporary in check_for_directory_rename()
  merge-ort: update comments to modern testfile location

"git diff --no-index" run inside a subdirectory under control of a
Git repository operated at the top of the working tree and stripped
the prefix from the output, and oddballs like "-" (stdin) did not
work correctly because of it.  Correct the set-up by undoing what
the set-up sequence did to cwd and prefix.

* jc/diff-no-index-in-subdir:
  diff: --no-index should ignore the worktree

Various options to "git diff" that makes comparison ignore certain
aspects of the differences (like "space changes are ignored",
"differences in lines that match these regular expressions are
ignored") did not work well with "--name-only" and friends.

* ly/diff-name-only-with-diff-from-content:
  diff: ensure consistent diff behavior with ignore options

Under a race against another process that is repacking the
repository, especially a partially cloned one, "git fetch" may
mistakenly think some objects we do have are missing, which has
been corrected.

* jk/fetch-check-graph-objects-fix:
  fetch-pack: re-scan when double-checking graph objects

"git repack --path-walk" lost objects in some corner cases, which
has been corrected.
cf. <CABPp-BHFxxGrqKc0m==TjQNjDGdO=H5Rf6EFsf2nfE1=TuraOQ@mail.gmail.com>

* ds/path-walk-repack-fix:
  path-walk: create initializer for path lists
  path-walk: fix setup of pending objects

Fixes multiple crashes around midx write-out codepaths.

* ds/midx-write-fixes:
  midx-write: simplify error cases
  midx-write: reenable signed comparison errors
  midx-write: use uint32_t for preferred_pack_idx
  midx-write: use cleanup when incremental midx fails
  midx-write: put failing response value back
  midx-write: only load initialized packs

A broken or malicious "git fetch" can say that it has the same
object for many many times, and the upload-pack serving it can
exhaust memory storing them redundantly, which has been corrected.

* ps/upload-pack-oom-protection:
  upload-pack: don't ACK non-commits repeatedly in protocol v2
  t5530: modernize tests

A corner case bug in "git log -L..." has been corrected.

* sg/line-log-boundary-fixes:
  line-log: show all line ranges touched by the same diff range
  line-log: fix assertion error

Some among "git add -p" and friends ignored color.diff and/or
color.ui configuration variables, which is an old regression, which
has been corrected.

* jk/add-i-color:
  contrib/diff-highlight: mention interactive.diffFilter
  add-interactive: manually fall back color config to color.ui
  add-interactive: respect color.diff for diff coloring
  stash: pass --no-color to diff plumbing child processes

"git rebase -i" failed to clean-up the commit log message when the
command commits the final one in a chain of "fixup" commands, which
has been corrected.

* pw/rebase-i-cleanup-fix:
  sequencer: remove VERBATIM_MSG flag
  rebase -i: respect commit.cleanup when picking fixups

Deal more gracefully with directory / file conflicts when the files
backend is used for ref storage, by failing only the ones that are
involved in the conflict while allowing others.

* kn/refs-files-case-insensitive:
  refs/files: handle D/F conflicts during locking
  refs/files: handle F/D conflicts in case-insensitive FS
  refs/files: use correct error type when lock exists
  refs/files: catch conflicts on case-insensitive file-systems

Doc update.

* kh/doc-git-log-markup-fix:
  doc: git-log: fix description list

Test fix for breakage introduced in Git 2.50.

* rj/t6137-cygwin-fix:
  t6137-*.sh: fix test failure on cygwin

Doc fix.

* kr/clone-synopsis-fix:
  docs: remove stray bracket from git-clone synopsis

Doc update.

* js/doc-sending-patch-via-thunderbird:
  doc/format-patch: adjust Thunderbird MUA hint to new add-on

Docfix.

* km/alias-doc-markup-fix:
  doc: fix formatting of function-wrap shell alias

Doc markup fixes.

* kh/doc-markup-fixes:
  doc: remove extra backtick for inline-verbatim
  doc: add missing backtick for inline-verbatim

Code clean-up.

* rs/object-name-extend-abbrev-len-update:
  object-name: declare pointer type of extend_abbrev_len()'s 2nd parameter

Docfix.

* mm/worktree-doc-typofix:
  docs: fix typo in worktree.adoc 'extension'

Doc mark-up fix.

* jc/doc-includeif-hasconfig-remote-url-fix:
  config: document includeIf conditions consistently

Doc update.

* ag/doc-sendmail-gmail-example-update:
  docs: update sendmail docs to use more secure SMTP server for Gmail

Code clean-up.

* ps/odb-clean-stale-wrappers:
  odb: drop deprecated wrapper functions

Doc update to describe a feature that has already been implemented.

* mh/doc-credential-url-prefix:
  docs/gitcredentials: describe URL prefix matching

Clarify the "--merge-base" command line option in "git merge-tree".

* en/doc-merge-tree-describe-merge-base:
  Documentation/git-merge-tree.adoc: clarify the --merge-base option

Documentation mark-up fix.

* ja/doc-markup-attached-paragraph-fix:
  doc: fix indentation of refStorage item in git-config(1)
  doc: change the markup of paragraphs following a nested list item

Documentation mark-up fix.

* kh/doc-patch-id-markup-fix:
  doc: patch-id: fix accidental literal blocks