parse-options: don't complete option aliases by default

Since 'OPT_ALIAS' was created in 5c38742 (parse-options: don't emit
"ambiguous option" for aliases, 2019-04-29), 'git clone
--git-completion-helper', which is used by the Bash completion script to
list options accepted by clone (via '__gitcomp_builtin'), lists both
'--recurse-submodules' and its alias '--recursive', which was not the
case before since '--recursive' had the PARSE_OPT_HIDDEN flag set, and
options with this flag are skipped by 'parse-options.c::show_gitcomp',
which implements 'git <cmd> --git-completion-helper'.

This means that typing 'git clone --recurs<TAB>' will yield both
'--recurse-submodules' and '--recursive', which is not ideal since both
do the same thing, and so the completion should directly complete the
canonical option.

At the point where 'show_gitcomp' is called in 'parse_options_step',
'preprocess_options' was already called in 'parse_options', so any
aliases are now copies of the original options with a modified help text
indicating they are aliases.

Helpfully, since 64cc539 (parse-options: don't leak alias help
messages, 2021-03-21) these copies have the PARSE_OPT_FROM_ALIAS flag
set, so check that flag early in 'show_gitcomp' and do not print them,
unless the user explicitely requested that *all* completion be shown (by
setting 'GIT_COMPLETION_SHOW_ALL'). After all, if we want to encourage
the use of '--recurse-submodules' over '--recursive', we'd better just
suggest the former.

The only other options alias is 'log' and friends' '--mailmap', which is
an alias for '--use-mailmap', but the Bash completion helpers for these
commands do not use '__gitcomp_builtin', and thus are unnaffected by
this change.

Test the new behaviour in t9902-completion.sh. As a side effect, this
also tests the correct behaviour of GIT_COMPLETION_SHOW_ALL, which was
not tested before. Note that since '__gitcomp_builtin' caches the
options it shows, we need to re-source the completion script to clear
that cache for the second test.

Signed-off-by: Philippe Blain <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: phil-blain

parse-options.c

@@ -585,7 +585,7 @@ static int show_gitcomp(const struct option *opts, int show_all)
 		if (!opts->long_name)
 			continue;
 		if (!show_all &&
-			(opts->flags & (PARSE_OPT_HIDDEN | PARSE_OPT_NOCOMPLETE)))
+			(opts->flags & (PARSE_OPT_HIDDEN | PARSE_OPT_NOCOMPLETE | PARSE_OPT_FROM_ALIAS)))
 			continue;
 
 		switch (opts->type) {

t/t9902-completion.sh

@@ -2404,6 +2404,19 @@ test_expect_success 'sourcing the completion script clears cached --options' '
 	verbose test -z "$__gitcomp_builtin_notes_edit"
 '
 
+test_expect_success 'option aliases are not shown by default' '
+	test_completion "git clone --recurs" "--recurse-submodules "
+'
+
+test_expect_success 'option aliases are shown with GIT_COMPLETION_SHOW_ALL' '
+	. "$GIT_BUILD_DIR/contrib/completion/git-completion.bash" &&
+	GIT_COMPLETION_SHOW_ALL=1 && export GIT_COMPLETION_SHOW_ALL &&
+	test_completion "git clone --recurs" <<-\EOF
+	--recurse-submodules Z
+	--recursive Z
+	EOF
+'
+
 test_expect_success '__git_complete' '
 	unset -f __git_wrap__git_main &&