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-http-fetch.txt

@@ -35,7 +35,7 @@ commit-id::
 
 --stdin::
 	Instead of a commit id on the command line (which is not expected in this
-	case), `git-http-fetch` expects lines on stdin in the format
+	case), 'git-http-fetch' expects lines on stdin in the format
 
 		<commit-id>['\t'<filename-as-in--w>]