doc: migrate git-commit manpage secondary files to new format

Signed-off-by: Jean-Noël Avila <jn.avila@free.fr>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/i18n.txt

@@ -34,7 +34,7 @@ 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' issue
+. `git commit` and `git commit-tree` issue
   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
@@ -50,7 +50,7 @@ of `i18n.commitEncoding` in their `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
+. `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

Documentation/signoff-option.txt

@@ -1,8 +1,8 @@
 ifdef::git-commit[]
--s::
+`-s`::
 endif::git-commit[]
---signoff::
---no-signoff::
+`--signoff`::
+`--no-signoff`::
 	Add a `Signed-off-by` trailer by the committer at the end of the commit
 	log message.  The meaning of a signoff depends on the project
 	to which you're committing.  For example, it may certify that
@@ -14,5 +14,5 @@ endif::git-commit[]
 	leadership of the project to which you're contributing to
 	understand how the signoffs are used in that project.
 +
-The --no-signoff option can be used to countermand an earlier --signoff
+The `--no-signoff` option can be used to countermand an earlier `--signoff`
 option on the command line.