stash: allow "stash show" diff output configurable

Some users might want to see diff (patch) output always rather than
diffstat when [s]he runs 'git stash show'.  Although this can be
done with adding -p option, users are too lazy to type extra three
keys.

Add two variables that control to show diffstat and patch output
respectively.  The stash.showStat is for diffstat and default is
true.  The stat.showPatch is for the patch output and default is
false.

Signed-off-by: Namhyung Kim <namhyung@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/config.txt

@@ -2476,6 +2476,16 @@ status.submoduleSummary::
 	submodule summary' command, which shows a similar output but does
 	not honor these settings.
 
+stash.showPatch::
+	If this is set to true, the `git stash show` command without an
+	option will show the stash in patch form.  Defaults to false.
+	See description of 'show' command in linkgit:git-stash[1].
+
+stash.showStat::
+	If this is set to true, the `git stash show` command without an
+	option will show diffstat of the stash.  Defaults to true.
+	See description of 'show' command in linkgit:git-stash[1].
+
 submodule.<name>.path::
 submodule.<name>.url::
 	The path within this project and URL for a submodule. These

Documentation/git-stash.txt

@@ -95,6 +95,8 @@ show [<stash>]::
 	shows the latest one. By default, the command shows the diffstat, but
 	it will accept any format known to 'git diff' (e.g., `git stash show
 	-p stash@{1}` to view the second most recent stash in patch form).
+	You can use stash.showStat and/or stash.showPatch config variables
+	to change the default behavior.
 
 pop [--index] [-q|--quiet] [<stash>]::
 

git-stash.sh

@@ -307,7 +307,25 @@ show_stash () {
 	ALLOW_UNKNOWN_FLAGS=t
 	assert_stash_like "$@"
 
-	git diff ${FLAGS:---stat} $b_commit $w_commit
+	if test -z "$FLAGS"
+	then
+		if test "$(git config --bool stash.showStat || echo true)" = "true"
+		then
+			FLAGS=--stat
+		fi
+
+		if test "$(git config --bool stash.showPatch || echo false)" = "true"
+		then
+			FLAGS=${FLAGS}${FLAGS:+ }-p
+		fi
+
+		if test -z "$FLAGS"
+		then
+			return 0
+		fi
+	fi
+
+	git diff ${FLAGS} $b_commit $w_commit
 }
 
 show_help () {