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

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

third_party/git/Documentation/i18n.txt

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+Git is to some extent character encoding agnostic.
+
+ - The contents of the blob objects are uninterpreted sequences
+   of bytes.  There is no encoding translation at the core
+   level.
+
+ - Path names are encoded in UTF-8 normalization form C. This
+   applies to tree objects, the index file, ref names, as well as
+   path names in command line arguments, environment variables
+   and config files (`.git/config` (see linkgit:git-config[1]),
+   linkgit:gitignore[5], linkgit:gitattributes[5] and
+   linkgit:gitmodules[5]).
++
+Note that Git at the core level treats path names simply as
+sequences of non-NUL bytes, there are no path name encoding
+conversions (except on Mac and Windows). Therefore, using
+non-ASCII path names will mostly work even on platforms and file
+systems that use legacy extended ASCII encodings. However,
+repositories created on such systems will not work properly on
+UTF-8-based systems (e.g. Linux, Mac, Windows) and vice versa.
+Additionally, many Git-based tools simply assume path names to
+be UTF-8 and will fail to display other encodings correctly.
+
+ - Commit log messages are typically encoded in UTF-8, but other
+   extended ASCII encodings are also supported. This includes
+   ISO-8859-x, CP125x and many others, but _not_ UTF-16/32,
+   EBCDIC and CJK multi-byte encodings (GBK, Shift-JIS, Big5,
+   EUC-x, CP9xx etc.).
+
+Although we encourage that the commit log messages are encoded
+in UTF-8, both the core and Git Porcelain are designed not to
+force UTF-8 on projects.  If all participants of a particular
+project find it more convenient to use legacy encodings, Git
+does not forbid it.  However, there are a few things to keep in
+mind.
+
+. 'git commit' and 'git commit-tree' issues
+  a warning if the commit log message given to it does not look
+  like a valid UTF-8 string, unless you explicitly say your
+  project uses a legacy encoding.  The way to say this is to
+  have i18n.commitencoding in `.git/config` file, like this:
++
+------------
+[i18n]
+	commitEncoding = ISO-8859-1
+------------
++
+Commit objects created with the above setting record the value
+of `i18n.commitEncoding` in its `encoding` header.  This is to
+help other people who look at them later.  Lack of this header
+implies that the commit log message is encoded in UTF-8.
+
+. 'git log', 'git show', 'git blame' and friends look at the
+  `encoding` header of a commit object, and try to re-code the
+  log message into UTF-8 unless otherwise specified.  You can
+  specify the desired output encoding with
+  `i18n.logOutputEncoding` in `.git/config` file, like this:
++
+------------
+[i18n]
+	logOutputEncoding = ISO-8859-1
+------------
++
+If you do not have this configuration variable, the value of
+`i18n.commitEncoding` is used instead.
+
+Note that we deliberately chose not to re-code the commit log
+message when a commit is made to force UTF-8 at the commit
+object level, because re-coding to UTF-8 is not necessarily a
+reversible operation.