[PATCH] support bash completion for add-on commands

[PATCH] support bash completion for add-on commands

[Joey Hess]

This makes it possible to implement bash completion for add-on commands,
that will work even when the bash completion scripts are being loaded
on-demand, as is done by the bash-completion package.

git's bash completion handles subcommands by running a _git_$command
function. As well as the many such functions included in
git-completion.bash, there can be other functions defined elsewhere
to support third-party add-on git commands, and they'll happily be used.

But, bash completion scripts are often loaded on demand, as shown in the
completion_loader example in bash's man page, and the bash-completion
implementation that is commonly used on many Linux systems. The demand
loading will load this very script from some place like
/usr/share/bash-completion/completions/git, when the user complete a git
command. But, completion scripts for git add-on commands don't get loaded.

For example, when I wrote a git-annex bash completion script,
bash was unable to tab complete "git annex foo", until I tab completed a
"git-annex" command. Which loaded the git-annex completion, and then
that same completion worked to make "git annex foo" tab complete. An
inconsistent UI..

So, if the git completion script is unable to find the wanted
_git_$command function, have it fall-back to looking for a git-$command
completion script, and loading it. The add-on script is looked for in the
same directory as the git completion script, which we can find by looking
at BASH_SOURCE.

Signed-off-by: Joey Hess <joeyh@joeyh.name>
---
 contrib/completion/git-completion.bash | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/contrib/completion/git-completion.bash b/contrib/completion/git-completion.bash
index c97c648..ba91b2a 100644
--- a/contrib/completion/git-completion.bash
+++ b/contrib/completion/git-completion.bash
@@ -2614,7 +2614,16 @@ __git_main ()
 	if [ -n "$expansion" ]; then
 		words[1]=$expansion
 		completion_func="_git_${expansion//-/_}"
-		declare -f $completion_func >/dev/null && $completion_func
+		declare -f $completion_func >/dev/null && $completion_func && return
+	fi
+
+	# As a fallback, if no completion function is defined for the
+	# command, look for add-on command completion script in same
+	# directory as this completion script, and if found, source it,
+	# and restart completion using it.
+	local compdir="${BASH_SOURCE%/*}"
+	if [ -e "$compdir/git-$command" ]; then
+		source "$compdir/git-$command" && __git_main "$@"
 	fi
 }
 

-- 
2.1.4