hub alias slows down prompt if using __git_ps1

[crobinso]

Using git-prompt.sh gives fancy shell prompts with git branch information, among other things:

https://github.com/git/git/blob/master/contrib/completion/git-prompt.sh

Example:

[crobinso@colepc src]$ cd qemu
[crobinso@colepc qemu (master)]$ touch foo && git add foo
[crobinso@colepc qemu (master +)]$

This is pretty popular with git users, and in fact fedora enables it by default when you install git.

If I add the hub git alias to my bashrc though, generating this prompt slows way down (which happens after every time a command is run):

Before hub alias

$ time eval echo "$PS1"
[u@h W (master *)]$

real    0m0.051s
user    0m0.003s
sys 0m0.041s

After hub alias:

$ time eval echo "$PS1"
[u@h W (master *)]$

real    0m0.317s
user    0m0.208s
sys 0m0.096s

I'm not sure if that measures it correctly, since it sure feels a lot longer than .3, but it's very noticable when previously the prompt seemed to refresh instantaneously.

I worked around this with a bit of shell in my bashrc, only talking to hub if the requested git command is one that hub overwrites. That hubcommands list would need to be expanded of course, I only added the functionality I care about. (also I'm not shell expert so I don't claim this to be a good solution, portable, etc)

function __git_or_hub {
    hubcommands="clone push pull-request fork"

    for i in "$@"; do
        test $(echo $i | cut -c 1) == "-" && continue
        cmdname="$i"
        break
    done

    for i in $hubcommands; do
        test "$i" == "$cmdname" && bincmd="hub" && break
    done

    test -z "$bincmd" && bincmd="git"

    $bincmd $@
}

# If github 'hub' is installed, use it as a git alias
#$(which hub > /dev/null 2>&1) && eval "$(hub alias -s)"
$(which hub > /dev/null 2>&1) && alias git='__git_or_hub'

[mislav]

Even better solution: have your prompt use command git instead of just git.

command goes straight to the command, avoiding aliases, functions.

[dougbarth]

I found slightly changing my PS1 to unalias git before running __git_ps1 made it skip the hub wrapper, but still left the alias intact for my input. The unalias doesn't affect the normal shell since the call to __git_ps1 is made in a subshell.

alias git=hub
export PS1='[\@ \u \w$(unalias git; __git_ps1)]\n$ '

[mislav]

I can see how unalias works, but it feels hackish and requires 2 commands instead of one. So I still prefer command git.

Calling stuff in one's prompt should be done with care. Each new command or function has potential to slow the prompt down further down the road. So I definitely suggest using command to go directly to the command and skip shell functions and aliases. It should be general practice.

Final thought: I won't fix this in hub (there's nothing to fix), but I will add a note about this in the docs and close this issue after that.

[ddeboer]

@mislav It's not clear to me how to replace __git_ps1 with a command git instance. Can you please elaborate?

[mislav]

@ddeboer I probably wasn't clear enough. If you were writing that function yourself, my suggestion was to be using command git everywhere instead of plain git invocations.

However, since this function is provided from somewhere else (git's own bash scripts?), you can't really edit it. So, your only option is to copy the function's source code over to your bash init files, and edit git in it to be command git. Or, you could use my bash prompt.

[ddeboer]

@mislav Thanks for the explanation!