manpages: italicize git command names (which were in teletype font)

The names of git commands are not meant to be entered at the
commandline; they are just names. So we render them in italics,
as is usual for command names in manpages.

Using

	doit () {
	  perl -e 'for (<>) { s/\`(git-[^\`.]*)\`/'\''\1'\''/g; print }'
	}
	for i in git*.txt config.txt diff*.txt blame*.txt fetch*.txt i18n.txt \
	        merge*.txt pretty*.txt pull*.txt rev*.txt urls*.txt
	do
	  doit <"$i" >"$i+" && mv "$i+" "$i"
	done
	git diff

.

Signed-off-by: Jonathan Nieder <jrnieder@uchicago.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-commit-tree.txt

@@ -70,7 +70,7 @@ is taken from the configuration items user.name and user.email, or, if not
 present, system user name and fully qualified hostname.
 
 A commit comment is read from stdin. If a changelog
-entry is not provided via "<" redirection, `git-commit-tree` will just wait
+entry is not provided via "<" redirection, 'git-commit-tree' will just wait
 for one to be entered and terminated with ^D.