post checkout hook gives error when using desktop app, but fine in cmd line

Description

I have a post-checkout hook.

When I use the command line the hook runs and the echo shows the message as expected

When I use the desktop I get an error message on checkout (see attached)

Version

GitHub Desktop version: 1.0.4

OS version: Microsoft Windows [Version 10.0.15063]

Steps to Reproduce

1. get a copy of https://github.com/MrAntix/github-desktop-hooks
2. install the hook (run install-hooks.bat)
3. open in desktop
4. checkout the other branch

Expected behavior: hook is run

Actual behavior: error - hook is not run

Reproduces how often: 100%

Logs

2017-10-16T11:30:56.993Z - info: [ui] launching: 1.0.4 (Windows 10.0.15063) 2017-10-16T11:31:00.758Z - error: [ui] git checkout --progress master -- exited with an unexpected code: 1. Your branch is up-to-date with ‘origin/master’.

Switched to branch ‘master’ error: cannot spawn .git/hooks/post-checkout: No such file or directory

Additional Information

[shiftkey]

This is an interesting side-effect of how we bundle Git in the app, and I needed to cast my mind back to this classic post.

Under the section “WHY WON’T GIT HOOKS WORK ON WINDOWS?”, we have this section:

On Unix-like OS’s, the #! tells the program loader that this is a script to be interpreted, and /bin/sh is the path to the interpreter you want to use, sh in this case. Windows is definitely not a Unix-like OS. Git for Windows supports Bash commands and shell scripts via Cygwin. By default, what does it find when it looks for sh.exe at /bin/sh? Yup, nothing; nothing at all.

What’s the fix?

Fix it by providing the path to the sh executable on your system.

As a workaround, these scripts can directly reference your Git installation, like so:

#!C:/Program\ Files/Git/usr/bin/sh.exe

That will work for you, but it’s not an actual solution. Git for Windows doesn’t set any other environment variables than the path to git.exe, so it might have some magic internals we need to mimic when we invoke Git inside the app (our version of Git is limited in features, but it does have sh.exe).

[shiftkey]

We can’t support bash.exe scripts on Windows currently because it’s not part of the Git installation we embed, but /bin/sh support should work once I get https://github.com/desktop/dugite/pull/141 merged and updated here.