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

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

third_party/git/Documentation/RelNotes/1.7.6.5.txt

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+Git v1.7.6.5 Release Notes
+==========================
+
+Fixes since v1.7.6.4
+--------------------
+
+ * The date parser did not accept timezone designators that lack minutes
+   part and also has a colon between "hh:mm".
+
+ * After fetching from a remote that has very long refname, the reporting
+   output could have corrupted by overrunning a static buffer.
+
+ * "git mergetool" did not use its arguments as pathspec, but as a path to
+   the file that may not even have any conflict.
+
+ * "git name-rev --all" tried to name all _objects_, naturally failing to
+   describe many blobs and trees, instead of showing only commits as
+   advertised in its documentation.
+
+ * "git remote rename $a $b" were not careful to match the remote name
+   against $a (i.e. source side of the remote nickname).
+
+ * "gitweb" used to produce a non-working link while showing the contents
+   of a blob, when JavaScript actions are enabled.
+
+Also contains minor fixes and documentation updates.