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-format-patch.txt

@@ -27,7 +27,7 @@ DESCRIPTION
 Prepare each commit with its patch in
 one file per commit, formatted to resemble UNIX mailbox format.
 The output of this command is convenient for e-mail submission or
-for use with `git-am`.
+for use with 'git-am'.
 
 There are two ways to specify which commits to operate on.
 
@@ -61,7 +61,7 @@ they are created in the current working directory.
 If -n is specified, instead of "[PATCH] Subject", the first line
 is formatted as "[PATCH n/m] Subject".
 
-If given --thread, `git-format-patch` will generate In-Reply-To and
+If given --thread, 'git-format-patch' will generate In-Reply-To and
 References headers to make the second and subsequent patch mails appear
 as replies to the first mail; this also generates a Message-Id header to
 reference.
@@ -187,7 +187,7 @@ EXAMPLES
 --------
 
 * Extract commits between revisions R1 and R2, and apply them on top of
-the current branch using `git-am` to cherry-pick them:
+the current branch using 'git-am' to cherry-pick them:
 +
 ------------
 $ git format-patch -k --stdout R1..R2 | git am -3 -k