po/git.pot: don't check in result of "make pot"

Remove the "po/git.pot" file from being tracked, which started with
dce37b66fb (l10n: initial git.pot for 1.7.10 upcoming release,
2012-02-13).

The reason the po/git.pot started being checked in was because the
po/*.po files were changed a schema where we'd generate them from a
known-good snapshot of po/git.pot, instead of each translator running
"make pot" themselves.

This makes sense, but we don't need to carry this file in-tree just to
achieve that aim, and doing so has resulted in a significant amount of
"diff churn" since this method of doing it was introduced:

    $ git log -p --oneline -- po/git.pot|wc -l
    553743

We can instead let l10n contributors to generate "po/git.pot" in runtime
to update their own "po/XX.po", and the l10n coordinator can check
pull requests using CI pipeline.

This reverts to the schema introduced initially in cd5513a716 (i18n:
Makefile: "pot" target to extract messages marked for translation,
2011-02-22).

The actual "git rm" of po/git.pot was in preceding commit to make this
change easier to review, and to preempt the mailing list from blocking
it due to it being too large.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Jiang Xin <zhiyou.jx@alibaba-inc.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Makefile

@@ -2786,8 +2786,8 @@ endef
 	$(call mkdir_p_parent_template)
 	$(QUIET_GEN)$(gen_pot_header)
 
-po/git.pot: .build/pot/git.header $(LOCALIZED_ALL_GEN_PO) FORCE
-	$(QUIET_GEN)$(MSGCAT) $(filter-out FORCE,$^) >$@
+po/git.pot: .build/pot/git.header $(LOCALIZED_ALL_GEN_PO)
+	$(QUIET_GEN)$(MSGCAT) $^ >$@
 
 .PHONY: pot
 pot: po/git.pot
@@ -3330,6 +3330,7 @@ cocciclean:
 
 clean: profile-clean coverage-clean cocciclean
 	$(RM) -r .build
+	$(RM) po/git.pot
 	$(RM) *.res
 	$(RM) $(OBJECTS)
 	$(RM) $(LIB_FILE) $(XDIFF_LIB) $(REFTABLE_LIB) $(REFTABLE_TEST_LIB)

po/.gitignore

@@ -1 +1,2 @@
 /build
+/git.pot