[PATCH v2] parse-options: don't complete option aliases by default

["Philippe Blain via GitGitGadget" <gitgitgadget@gmail.com>]

From: Philippe Blain <levraiphilippeblain@gmail.com>

Since 'OPT_ALIAS' was created in 5c387428f1 (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 64cc539fd2 (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 <levraiphilippeblain@gmail.com>
---
    parse-options: don't complete option aliases by default
    
    Changes since v1:
    
     * Added a paragraph to the commit message to clarify that the goal of
       this patch is to have the completion show only the canonical option
       and not its alias.

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-996%2Fphil-blain%2Fclone-recurse-completion-v2
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-996/phil-blain/clone-recurse-completion-v2
Pull-Request: https://github.com/gitgitgadget/git/pull/996

Range-diff vs v1:

 1:  091a59323b7 ! 1:  9ae43e17e0c parse-options: don't complete option aliases by default
     @@ Commit message
          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


 parse-options.c       |  2 +-
 t/t9902-completion.sh | 13 +++++++++++++
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/parse-options.c b/parse-options.c
index e6f56768ca5..2abff136a17 100644
--- a/parse-options.c
+++ b/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) {
diff --git a/t/t9902-completion.sh b/t/t9902-completion.sh
index cb057ef1613..11573936d58 100755
--- a/t/t9902-completion.sh
+++ b/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 &&
 

base-commit: d486ca60a51c9cb1fe068803c3f540724e95e83a
-- 
gitgitgadget