Adding external subcommands to Git is as easy as to put an executable file git-foo into PATH. Packaging such subcommands for a Linux distribution can be achieved by unpacking the executable into /usr/bin of the user's system. Adding system-wide completion scripts for new subcommands, however, can be a bit tricky.
Since bash-completion started to use dynamical loading of completion scripts since v1.90 (preview of v2.0), it is no longer sufficient to drop a completion script of a subcommand into the standard completions path, /usr/share/bash-completion/completions, since this script will not be loaded if called as a git subcommand. For example, look at https://bugs.gentoo.org/544722. To give a short summary: The popular git-flow subcommand provides a completion script, which gets installed as /usr/share/bash-completion/completions/git-flow. If you now type into a Bash shell: git flow <TAB> You will not get any completions, because bash-completion only loads completions for git and git has no idea that git-flow is defined in another file. You have to load this script manually or trigger the dynamic loader with: git-flow <TAB> # Please notice the dash instead of whitespace This will not complete anything either, because it only defines a Bash function, without generating completions. But now the correct completion script has been loaded and the first command can use the completions. So, the goal is now to teach the git completion script to consider the possibility of external completion scripts for subcommands, but of course without breaking current workflows. I think the easiest method is to use a function that was defined by bash-completion v1.90, namely _completion_loader. It will take care of loading the correct script if present. Afterwards, the git completion script behaves as usual. _completion_loader was introduced in commit 20c05b43 of bash-completion (https://github.com/scop/bash-completion.git) back in 2011, so it should be available in even older LTS distributions. This function searches for external completion scripts not only in the default path /usr/share/bash-completion/completions, but also in the user's home directory via $XDG_DATA_HOME and in a user specified directory via $BASH_COMPLETION_USER_DIR. The only "drawback" (if it even can be called as such) is, that if _completion_loader does not find a completion script, it automatically registers a minimal function for basic path completion. In practice, however, this will not matter, because in this case the given command is a git command in its dashed form, e.g. 'git-diff-index', and those have been deprecated for a long time. This way we can leverage bash-completion's dynamic loading for git subcommands and make it easier for developers to distribute custom completion scripts. Signed-off-by: Florian Gamböck <m...@floga.de> --- contrib/completion/git-completion.bash | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/contrib/completion/git-completion.bash b/contrib/completion/git-completion.bash index b09c8a236..604ba2b03 100644 --- a/contrib/completion/git-completion.bash +++ b/contrib/completion/git-completion.bash @@ -3096,12 +3096,22 @@ __git_main () fi local completion_func="_git_${command//-/_}" + if ! declare -f $completion_func >/dev/null 2>/dev/null && + declare -f _completion_loader >/dev/null 2>/dev/null + then + _completion_loader "git-$command" + fi declare -f $completion_func >/dev/null 2>/dev/null && $completion_func && return local expansion=$(__git_aliased_command "$command") if [ -n "$expansion" ]; then words[1]=$expansion completion_func="_git_${expansion//-/_}" + if ! declare -f $completion_func >/dev/null 2>/dev/null && + declare -f _completion_loader >/dev/null 2>/dev/null + then + _completion_loader "git-$expansion" + fi declare -f $completion_func >/dev/null 2>/dev/null && $completion_func fi } -- 2.16.1
