Makefile: add "po-init" rule to initialize po/XX.po

The core translation is the minimum set of work that must be done for a
new language translation.

There are over 5000 messages in the template message file "po/git.pot"
that need to be translated. It is not a piece of cake for such a huge
workload. So we used to define a small set of messages called "core
translation" that a new l10n contributor must complete before sending
pull request to the l10n coordinator.

By pulling in some parts of the git-po-helper[^1] logic, we add a new
rule to create this core translation message "po/git-core.pot":

    make po/git-core.pot

To help new l10n contributors to initialized their "po/XX.pot" from
"po/git-core.pot", we also add new rules "po-init":

    make po-init PO_FILE=po/XX.po

[^1]: https://github.com/git-l10n/git-po-helper/

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

3 files changed, 41 insertions, 1 deletions

diff --git a/Makefile b/Makefile
index efd242b255..0a5b4b4ede 100644
--- a/Makefile
+++ b/Makefile
@@ -2806,6 +2806,7 @@ po-update: po/git.pot
 	$(check_po_file_envvar)
 	@if test ! -e $(PO_FILE); then \
 		echo >&2 "error: $(PO_FILE) does not exist"; \
+		echo >&2 'To create an initial po file, use: "make po-init PO_FILE=po/XX.po"'; \
 		exit 1; \
 	fi
 	$(QUIET_MSGMERGE)$(MSGMERGE) $(MSGMERGE_FLAGS) $(PO_FILE) po/git.pot
@@ -2813,6 +2814,43 @@ po-update: po/git.pot
 .PHONY: check-pot
 check-pot: $(LOCALIZED_ALL_GEN_PO)
 
+### TODO FIXME: Translating everything in these files is a bad
+### heuristic for "core", as we'll translate obscure error() messages
+### along with commonly seen i18n messages. A better heuristic would
+### be to e.g. use spatch to first remove error/die/warning
+### etc. messages.
+LOCALIZED_C_CORE =
+LOCALIZED_C_CORE += builtin/checkout.c
+LOCALIZED_C_CORE += builtin/clone.c
+LOCALIZED_C_CORE += builtin/index-pack.c
+LOCALIZED_C_CORE += builtin/push.c
+LOCALIZED_C_CORE += builtin/reset.c
+LOCALIZED_C_CORE += remote.c
+LOCALIZED_C_CORE += wt-status.c
+
+LOCALIZED_C_CORE_GEN_PO = $(LOCALIZED_C_CORE:%=.build/pot/po/%.po)
+
+.build/pot/git-core.header: $(LOCALIZED_C_CORE_GEN_PO)
+	$(call mkdir_p_parent_template)
+	$(QUIET_GEN)$(gen_pot_header)
+
+po/git-core.pot: .build/pot/git-core.header $(LOCALIZED_C_CORE_GEN_PO)
+	$(QUIET_GEN)$(MSGCAT) $^ >$@
+
+.PHONY: po-init
+po-init: po/git-core.pot
+	$(check_po_file_envvar)
+	@if test -e $(PO_FILE); then \
+		echo >&2 "error: $(PO_FILE) exists already"; \
+		exit 1; \
+	fi
+	$(QUIET_MSGINIT)msginit \
+		--input=$< \
+		--output=$(PO_FILE) \
+		--no-translator \
+		--locale=$(PO_FILE:po/%.po=%)
+
+## po/*.po files & their rules
 ifdef NO_GETTEXT
 POFILES :=
 MOFILES :=
@@ -3348,7 +3386,7 @@ cocciclean:
 
 clean: profile-clean coverage-clean cocciclean
 	$(RM) -r .build
-	$(RM) po/git.pot
+	$(RM) po/git.pot po/git-core.pot
 	$(RM) *.res
 	$(RM) $(OBJECTS)
 	$(RM) $(LIB_FILE) $(XDIFF_LIB) $(REFTABLE_LIB) $(REFTABLE_TEST_LIB)
diff --git a/po/.gitignore b/po/.gitignore
index 37d1301b32..ff0e5176a6 100644
--- a/po/.gitignore
+++ b/po/.gitignore
@@ -1,2 +1,3 @@
 /build
 /git.pot
+/git-core.pot
diff --git a/shared.mak b/shared.mak
index 8cd170a7e7..4330192e9c 100644
--- a/shared.mak
+++ b/shared.mak
@@ -62,6 +62,7 @@ ifndef V
 	QUIET_BUILT_IN = @echo '   ' BUILTIN $@;
 	QUIET_LNCP     = @echo '   ' LN/CP $@;
 	QUIET_XGETTEXT = @echo '   ' XGETTEXT $@;
+	QUIET_MSGINIT  = @echo '   ' MSGINIT $@;
 	QUIET_MSGFMT   = @echo '   ' MSGFMT $@;
 	QUIET_MSGMERGE = @echo '   ' MSGMERGE $@;
 	QUIET_GCOV     = @echo '   ' GCOV $@;