Documentation: wrap blocks with "--"

The documentation for each of these options contains a list. After the
list, AsciiDoc interprets the continuation as a continuation of the
*list*, not as a continution of the larger block. As a result, we get
too much indentation. Wrap the entire blocks in "--" to fix this. With
Asciidoctor, this commit is a no-op, and the two programs now render
these identically.

These two files share the same problem and indeed, they both document
`--untracked-files` in quite similar ways. I haven't checked to what
extent that is intentional or warranted, and to what extent they have
simply drifted apart. I consider such an investigation and possible
cleanup as out of scope for this commit and this patch series.

Signed-off-by: Martin Ågren <martin.agren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-commit.txt

@@ -282,18 +282,20 @@ FROM UPSTREAM REBASE" section in linkgit:git-rebase[1].)
 --untracked-files[=<mode>]::
 	Show untracked files.
 +
+--
 The mode parameter is optional (defaults to 'all'), and is used to
 specify the handling of untracked files; when -u is not used, the
 default is 'normal', i.e. show untracked files and directories.
-+
+
 The possible options are:
-+
+
 	- 'no'     - Show no untracked files
 	- 'normal' - Shows untracked files and directories
 	- 'all'    - Also shows individual files in untracked directories.
-+
+
 The default can be changed using the status.showUntrackedFiles
 configuration variable documented in linkgit:git-config[1].
+--
 
 -v::
 --verbose::