Add post-checkout

[andrewhare]

This adds support for the post-checkout hook.

Fixes: #1120
Documentation PR: pre-commit/pre-commit.com#307

One thing I would still like to do, if possible, would be to force hooks like this to always have always_run be set since that is somewhat implied by the nature of the hook (since it doesn't operate on files).

[asottile]

will have to fix CI but this is a good start

[asottile]

I think we could potentially reuse --source / --origin for these arguments?

[andrewhare]

I can do that if you want to keep the arg count down. However, I don't think that source/origin maps directly to new-head-ref/prev-head-ref so it might create some confusion. I'll leave that decision up to you.

[asottile]

source / origin is a "from ref" -> "to ref" relation, so I think it fits well enough

[andrewhare]

Ok cool, I will do that.

[asottile]

since these are only used once, it probably makes sense to inline them adjacent to the test itself

[andrewhare]

Do you want me to inline the entire fixture into the test or just the git add / git commit part?

[asottile]

ah mostly that there isn't a reason to put it in conftest.py unless it is being shared across multiple tests

[andrewhare]

Sounds good to me, I will move it.

[andrewhare]

Thanks for the feedback, I will fix the CI issues later today.

[andrewhare]

@asottile I made the changes you requested and CI is now green as well, please take another look when you can.

[asottile]

thanks again for working on this!

[andrewhare]

Yeah, your welcome! It’s was fun, you’ve got a great project. Thanks for all your input!

…

On Sun, Feb 23, 2020 at 10:24 AM Anthony Sottile ***@***.***> wrote: ***@***.**** approved this pull request. thanks again for working on this! <https://camo.githubusercontent.com/da817a3f4b192dfb496051a9aba8111fb546ef29/68747470733a2f2f692e666c756666792e63632f673654523052564a4d4a3466356e577244523339744e7264646333674e53646d2e676966> — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#1339?email_source=notifications&email_token=AAAQKANQQH36CAF2RZ2YQF3REK5L7A5CNFSM4KYWLCFKYY3PNVWWK3TUL52HS4DFWFIHK3DMKJSXC5LFON2FEZLWNFSXPKTDN5WW2ZLOORPWSZGOCWSKWZA#pullrequestreview-363113316>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAAQKALKSGBO55A3EQFZUXDREK5L7ANCNFSM4KYWLCFA> .

[asottile]

I'm also going to follow up and add aliases for --source and --origin, probably --from-ref and --to-ref since the current names are definitely confusing 😆

[asottile]

just played with this a bit, not sure if it's intentional but the post-checkout hooks are currently getting the list of files different between the two branches

I think they're not supposed to get any files at all so I'm making a change to fix that 👍

[asottile]

$ ~/workspace/pre-commit/venv/bin/pre-commit install -t post-checkout
pre-commit installed at .git/hooks/post-checkout
$ git add .
$ git commit -m 'add config'
[master (root-commit) d15280a] add config
 1 file changed, 5 insertions(+)
 create mode 100644 .pre-commit-config.yaml
$ git status
On branch master
nothing to commit, working tree clean
$ git status
On branch master
nothing to commit, working tree clean
$ git checkout master -b wat
Switched to a new branch 'wat'
identity.............................................(no files to check)Skipped
- hook id: identity
$ touch foo.py
$ git status
On branch wat
Untracked files:
	foo.py

nothing added to commit but untracked files present
$ git add .
$ git commit -m "add foo"
[wat 1ca3ef0] add foo
 1 file changed, 0 insertions(+), 0 deletions(-)
 create mode 100644 foo.py
$ git checkout master 
Switched to branch 'master'
identity.............................................(no files to check)Skipped
- hook id: identity
$ git checkout wat
Switched to branch 'wat'
identity.................................................................Passed
- hook id: identity
- duration: 0.04s

foo.py

$ cat .pre-commit-config.yaml 
repos:
-   repo: meta
    hooks:
    -   id: identity
        stages: [post-checkout]        

[asottile]

#1344 for that one!

[andrewhare]

@asottile Nice catch on not needing the files, I missed that!

#1344 looks like a great fix.

[asottile]

oh right -- this got released as part of 2.2.0 -- thanks again for the patch!