pretty: test --expand-tabs

The test prepares a simple commit with HT on its log message lines,
and makes sure that

 - formats that should or should not expand tabs by default do or do
   not expand tabs respectively,

 - with explicit --expand-tabs=<N> and short-hands --expand-tabs
   (equivalent to --expand-tabs=8) and --no-expand-tabs (equivalent
   to --expand-tabs=0) before or after the explicit --pretty=$fmt,
   the tabs are expanded (or not expanded) accordingly.

The tests use the second line of the log message for formats other
than --pretty=short, primarily because the first line of the email
format is handled specially to add the [PATCH] prefix, etc. in a
separate codepath (--pretty=short uses the first line because there
is no other line to test).

Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t4213-log-tabexpand.sh

@@ -0,0 +1,105 @@
+#!/bin/sh
+
+test_description='log/show --expand-tabs'
+
+. ./test-lib.sh
+
+HT="	"
+title='tab indent at the beginning of the title line'
+body='tab indent on a line in the body'
+
+# usage: count_expand $indent $numSP $numHT @format_args
+count_expand ()
+{
+	expect=
+	count=$(( $1 + $2 )) ;# expected spaces
+	while test $count -gt 0
+	do
+		expect="$expect "
+		count=$(( $count - 1 ))
+	done
+	shift 2
+	count=$1 ;# expected tabs
+	while test $count -gt 0
+	do
+		expect="$expect$HT"
+		count=$(( $count - 1 ))
+	done
+	shift
+
+	# The remainder of the command line is "git show -s" options
+	case " $* " in
+	*' --pretty=short '*)
+		line=$title ;;
+	*)
+		line=$body ;;
+	esac
+
+	# Prefix the output with the command line arguments, and
+	# replace SP with a dot both in the expecte and actual output
+	# so that test_cmp would show the differene together with the
+	# breakage in a way easier to consume by the debugging user.
+	{
+		echo "git show -s $*"
+		echo "$expect$line"
+	} | sed -e 's/ /./g' >expect
+
+	{
+		echo "git show -s $*"
+		git show -s "$@" |
+		sed -n -e "/$line\$/p"
+	} | sed -e 's/ /./g' >actual
+
+	test_cmp expect actual
+}
+
+test_expand ()
+{
+	fmt=$1
+	case "$fmt" in
+	*=raw | *=short | *=email)
+		default="0 1" ;;
+	*)
+		default="8 0" ;;
+	esac
+	case "$fmt" in
+	*=email)
+		in=0 ;;
+	*)
+		in=4 ;;
+	esac
+	test_expect_success "expand/no-expand${fmt:+ for $fmt}" '
+		count_expand $in $default $fmt &&
+		count_expand $in 8 0 $fmt --expand-tabs &&
+		count_expand $in 8 0 --expand-tabs $fmt &&
+		count_expand $in 8 0 $fmt --expand-tabs=8 &&
+		count_expand $in 8 0 --expand-tabs=8 $fmt &&
+		count_expand $in 0 1 $fmt --no-expand-tabs &&
+		count_expand $in 0 1 --no-expand-tabs $fmt &&
+		count_expand $in 0 1 $fmt --expand-tabs=0 &&
+		count_expand $in 0 1 --expand-tabs=0 $fmt &&
+		count_expand $in 4 0 $fmt --expand-tabs=4 &&
+		count_expand $in 4 0 --expand-tabs=4 $fmt
+	'
+}
+
+test_expect_success 'setup' '
+	test_tick &&
+	sed -e "s/Q/$HT/g" <<-EOF >msg &&
+	Q$title
+
+	Q$body
+	EOF
+	git commit --allow-empty -F msg
+'
+
+test_expand ""
+test_expand --pretty
+test_expand --pretty=short
+test_expand --pretty=medium
+test_expand --pretty=full
+test_expand --pretty=fuller
+test_expand --pretty=raw
+test_expand --pretty=email
+
+test_done