Better errors - git fails with a confusing error message when a commit doesn't exist in a git repo, used in a stack.yaml config

[athanclark]

Hello everybody, this is a casual issue and not immediately detrimental.

In a stack.yaml, if you set a source code location to a git commit that doesn't exist on the referenced repo, then you get the "could not parse object" error, which led me to believe I had somehow pasted my commit hash wrong. For instance, if you have this in your stack.yaml:

packages:
- '.'
- location:
    git: https://github.com/athanclark/foo
    commit: 8e22ca206e9fc8fd7b903afa8b073120f8897793
  extra-dep: true

and you tried to stack build, you would get the error:

Running /usr/bin/git reset --hard 8e22ca206e9fc8fd7b903afa8b073120f8897793 exited with ExitFailure 128

fatal: Could not parse object '8e22ca206e9fc8fd7b903afa8b073120f8897793'.

Which is misleading.

[mgsloan]

It'd make sense to me to add a message like Please ensure that commit 8e22ca206e9fc8fd7b903afa8b073120f8897793 exists within https://github.com/athanclark/foo when that command fails (but also provide the command output).

[mrkkrp]

@mgsloan, Where this thing is processed? Where should one start to look to add this message?

[mgsloan]

@mrkkrp here

[mgsloan]

It's fixed, thanks @mrkkrp

Running /usr/bin/git reset --hard 8e22ca206e9fc8fd7b903afa8b073120f8897793 exited with ExitFailure 128

fatal: Could not parse object '8e22ca206e9fc8fd7b903afa8b073120f8897793'.

Please ensure that commit 8e22ca206e9fc8fd7b903afa8b073120f8897793 exists within https://github.com/ekmett/lens