gettext: add gettextln, eval_gettextln to encode common idiom

Currently, if you want to use gettext or eval_gettext to format a message
you may have to add a separate echo statement and a surrounding subshell
in order to interpolate the required trailing new line.

This patch introduces two new helper functions, gettextln and eval_gettextln
which append a trailing newline to the gettext output.

This allows constructions of the form:

	if test -s "$GIT_DIR/BISECT_START"
	then
		(
			gettext "You need to give me at least one good and one bad revisions.
(You can use \"git bisect bad\" and \"git bisect good\" for that.)" &&
			echo
		) >&2
	else
	...

to be expressed more concisely as:

	if test -s "$GIT_DIR/BISECT_START"
	then
		gettextln "You need to give me at least one good and one bad revisions.
(You can use \"git bisect bad\" and \"git bisect good\" for that.)" >&2
	else
	...

Acked-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Jon Seymour <jon.seymour@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

git-sh-i18n.sh

@@ -11,19 +11,38 @@ then
 		printf "%s" "$1"
 	}
 
+	gettextln() {
+		printf "%s\n" "$1"
+	}
+
 	eval_gettext () {
 		printf "%s" "$1" | (
 			export PATH $(git sh-i18n--envsubst --variables "$1");
 			git sh-i18n--envsubst "$1"
 		)
 	}
+
+	eval_gettextln () {
+		printf "%s\n" "$1" | (
+			export PATH $(git sh-i18n--envsubst --variables "$1");
+			git sh-i18n--envsubst "$1"
+		)
+	}
 else
 	gettext () {
 		printf "%s" "# GETTEXT POISON #"
 	}
 
+	gettextln () {
+		printf "%s\n" "# GETTEXT POISON #"
+	}
+
 	eval_gettext () {
 		printf "%s" "# GETTEXT POISON #"
 	}
+
+	eval_gettextln () {
+		printf "%s\n" "# GETTEXT POISON #"
+	}
 fi