i18n: add no-op _() and N_() wrappers

The _ function is for translating strings into the user's chosen
language.  The N_ macro just marks translatable strings for the
xgettext(1) tool without translating them; it is intended for use in
contexts where a function call cannot be used.  So, for example:

	fprintf(stderr, _("Expansion of alias '%s' failed; "
		"'%s' is not a git command\n"),
		cmd, argv[0]);

and

	const char *unpack_plumbing_errors[NB_UNPACK_TREES_ERROR_TYPES] = {
		/* ERROR_WOULD_OVERWRITE */
		N_("Entry '%s' would be overwritten by merge. Cannot merge."),
	[...]

Define such _ and N_ in a new gettext.h and include it in cache.h, so
they can be used everywhere.  Each just returns its argument for now.
_ is a function rather than a macro like N_ to avoid the temptation to
use _("foo") as a string literal (which would be a compile-time error
once _(s) expands to an expression for the translation of s).

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/Makefile b/Makefile
index ade79232f..c153f450c 100644
--- a/Makefile
+++ b/Makefile
@@ -515,6 +515,7 @@ LIB_H += diff.h
 LIB_H += dir.h
 LIB_H += exec_cmd.h
 LIB_H += fsck.h
+LIB_H += gettext.h
 LIB_H += git-compat-util.h
 LIB_H += graph.h
 LIB_H += grep.h