[ENH] add a .git-blame-ignore-revs to ignore formatting PR from git blame

[Remi-Gau]

Is there an existing issue for this?

• I have searched the existing issues

Describe your proposed enhancement in detail.

Came across while browsing the black documentation:
https://black.readthedocs.io/en/stable/guides/introducing_black_to_your_project.html#avoiding-ruining-git-blame

One problem with all the reformating PRs is that they make reduce the usefulness (or at least add more friction) to the use of git blame to trace change was introduced when: black may end up touching many if not most lines in the code base and git blame may invariably point to one of those reformatting PRs when we use it, even though it very unlikely that a behavioral change came from them.

Using a .git-blame-ignore-revs could allow to "skip" to PR during a git blame call.

• ignore PRs for f strings ?

Benefits to the change

Ideally this should facilitate the tracking down of changes in the code base by ignoring changes that pure reformatting and do not entail functional change.

[Remi-Gau]

Let me know what you think.

[Remi-Gau]

Also it seems to also work when using git blame via the github interface: https://github.blog/changelog/2022-03-24-ignore-commits-in-the-blame-view-beta/

[ymzayek]

I already feel that it's a bit slower to track down changes so I would be for this, but I haven't used it before. What would be the downside if any?

[NicolasGensollen]

I never used it but I'm +1 on this.
The risk and cost seem very small and I can clearly see the benefits of having a meaningful blame where @Remi-Gau isn't responsible for all the bugs of Nilearn 😉.

[Remi-Gau]

I can clearly see the benefits of having a meaningful blame where @Remi-Gau isn't responsible for all the bugs of Nilearn

Rémi then proceeds to blame-ignore ALL the PRs he ever authored... 😜

[Remi-Gau]

See this comment: #3701 (comment)

Also keep this issue opened until most of the reformatting is not over

[Remi-Gau]

Related to #3701 (comment)

 git blame --ignore-revs-file .git-blame-ignore-revs nilearn/image/resampling.py 

copy paste of a comment from #3755

Still shows content from 3651 event though it is supposed to be ignored:

# run isort and flake8 on the whole nilearn code base in CI (#3651)
44933309ecd09add795ce1c3ea5edaab4294da87

More annoyingly it is also still the case for:

 git blame --ignore-rev 44933309  nilearn/image/resampling.py

[ghisvail]

We use one of these in Clinica.

[ymzayek]

To add:

#4147 25c456f34d45409f07dcca560e45f892a05dde4b
#4146 724cd51672417fd7db1e11c0f755178130df9feb
#4145 e083dba365ebf6a60bc9cd2e6b979030c769e4bf
#4144 7d4d7f3a343c68ed44e0d356b65ba78af4444f3a

[Remi-Gau]

Thanks.
Though I am still at a loss to actually make this git blame ignore work as I think it should.

[ymzayek]

I'm also unsure of how to make it work :/ If I get a chance I'll look into it some more