t9902: protect test from stray build artifacts

When you have random build artifacts in your build directory, left
behind by running "make" while on another branch, the "git help -a"
command run by __git_list_all_commands in the completion script that
is being tested does not have a way to know that they are not part
of the subcommands this build will ship.  Such extra subcommands may
come from the user's $PATH.  They will interfere with the tests that
expect a certain prefix to uniquely expand to a known completion.

Instrument the completion script and give it a way for us to tell
what (subset of) subcommands we are going to ship.

Also add a test to "git --help <prefix><TAB>" expansion.  It needs
to show not just commands but some selected documentation pages.

Based on an idea by Jeff King.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 10 insertions, 1 deletions

diff --git a/contrib/completion/git-completion.bash b/contrib/completion/git-completion.bash
index a4c48e179..6139b5011 100644
--- a/contrib/completion/git-completion.bash
+++ b/contrib/completion/git-completion.bash
@@ -531,10 +531,19 @@ __git_complete_strategy ()
 	return 1
 }
 
+__git_commands () {
+	if test -n "${GIT_TESTING_COMMAND_COMPLETION:-}"
+	then
+		printf "%s" "${GIT_TESTING_COMMAND_COMPLETION}"
+	else
+		git help -a|egrep '^  [a-zA-Z0-9]'
+	fi
+}
+
 __git_list_all_commands ()
 {
 	local i IFS=" "$'\n'
-	for i in $(git help -a|egrep '^  [a-zA-Z0-9]')
+	for i in $(__git_commands)
 	do
 		case $i in
 		*--*)             : helper pattern;;