Merge branch 'jc/no-update-fetch-head'

"git fetch" learned --no-write-fetch-head option to avoid writing
the FETCH_HEAD file.

* jc/no-update-fetch-head:
  fetch: optionally allow disabling FETCH_HEAD update

Documentation/fetch-options.txt

@@ -64,6 +64,15 @@ documented in linkgit:git-config[1].
 --dry-run::
 	Show what would be done, without making any changes.
 
+ifndef::git-pull[]
+--[no-]write-fetch-head::
+	Write the list of remote refs fetched in the `FETCH_HEAD`
+	file directly under `$GIT_DIR`.  This is the default.
+	Passing `--no-write-fetch-head` from the command line tells
+	Git not to write the file.  Under `--dry-run` option, the
+	file is never written.
+endif::git-pull[]
+
 -f::
 --force::
 	When 'git fetch' is used with `<src>:<dst>` refspec it may