merge(third_party/git): Merge squashed git subtree at v2.23.0

Merge commit '1b593e1ea4' as 'third_party/git'

third_party/git/Documentation/RelNotes/1.7.4.4.txt

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+Git v1.7.4.4 Release Notes
+==========================
+
+Fixes since v1.7.4.3
+--------------------
+
+ * Compilation of sha1_file.c on BSD platforms were broken due to our
+   recent use of getrlimit() without including <sys/resource.h>.
+
+ * "git config" did not diagnose incorrect configuration variable names.
+
+ * "git format-patch" did not wrap a long subject line that resulted from
+   rfc2047 encoding.
+
+ * "git instaweb" should work better again with plackup.
+
+ * "git log --max-count=4 -Sfoobar" now shows 4 commits that changes the
+   number of occurrences of string "foobar"; it used to scan only for 4
+   commits and then emitted only matching ones.
+
+ * "git log --first-parent --boundary $c^..$c" segfaulted on a merge.
+
+ * "git pull" into an empty branch should have behaved as if
+   fast-forwarding from emptiness to the version being pulled, with
+   the usual protection against overwriting untracked files.
+
+ * "git submodule" that is run while a merge in the superproject is in
+   conflicted state tried to process each conflicted submodule up to
+   three times.
+
+ * "git status" spent all the effort to notice racily-clean index entries
+   but didn't update the index file to help later operations go faster in
+   some cases.
+
+And other minor fixes and documentation updates.