Add support for Git Revision List files

[Nixinova]

• Resolve Add git-blame-ignore-revs #5901

Description

Adds the simple git-blame-ignore-revs file format, which is just a list of commit hashes with hash-comments allowed.

Checklist:

• I am adding a new language.
  • The extension of the new language is used in hundreds of repositories on GitHub.com.
    • Search results for each extension:
      • filename:git-blame-ignore-revs: 3.9K+ results, 3.1K in root (±1K because GitHub search is screwy)
  • I have included a real-world usage sample for all extensions added in this PR:
    • Sample: .git-blame-ignore-revs, license MIT
  • I have included a syntax highlighting grammar:
    • grammar repo
    • Preview (I revived Lightshow)
  • I have updated the heuristics to distinguish my language from others using the same extension.

Not sure whether the submodule updating was committed.

[lildude]

🤔 does this really need its own entry? Why not add it to the list of files under the “Ignore List”? From a quick test it highlights fine.

[Nixinova]

does this really need its own entry? Why not add it to the list of files under the “Ignore List”? From a quick test it highlights fine.

I defaulted to using a separate language so it could have the invalid content highlighting but I can change it to be under Ignore-List if you would prefer that.

---

```git-blame-ignore

```ignore-list

[lildude]

I hadn't considered invalid syntax, but now you mention it, it looks like the current gitignore grammar doesn't handle invalid syntax either so maybe it's worth updating that instead?

[Alhadis]

so maybe it's worth updating that instead?

@lildude The grammar used to highlight .gitignore files is actually responsible for highlighting several nearly-identical filetypes, most of them deliberately modelled off the familiar gitignore(5) format.

For that reason, I'd advise against enforcing any lexical integrity via highlighting, especially since whitespace in a gitignore(5) pattern may be intentional (and therefore impossible to disambiguate from a legitimate error in other contexts):

pathname with spaces/

[Alhadis]

@Nixinova I've sent you a pull-request to correct a few remaining highlighting issues, as well as to rename the grammar for the reasons I explained earlier. Your PR will need to be updated to reflect the outcome of that PR.