tools: avoid fetch extra commits when validating commit messages

[aduh95]

We only need the number of commits in the PR, plus one for the merge commit.
I couldn't figure out a way to compute the + 1 operation without an extra step, if someone knows a cleaner way please chime in.

[mmarchini]

lgtm (if something goes wrong we can always revert)

[mmarchini]

Actually, can you force two commits here to demonstrate that it works?

[Mesteery]

plus one for the merge commit.

Which merge commit?

[aduh95]

plus one for the merge commit.

Which merge commit?

The commit the merges the PR branch into the target branch. I tried to find reference for that in GH Actions docs but couldn't find it.

[targos]

The commit the merges the PR branch into the target branch. I tried to find reference for that in GH Actions docs but couldn't find it.

What kind of message does that commit have? Do we skip its validation?

[Mesteery]

Btw, I don't understand how it can work on a push. pull_request.commits is only available on a pull request.

[targos]

Btw, I don't understand how it can work on a push. pull_request.commits is only available on a pull request.

This workflow only runs on the pull_request event.

[Mesteery]

Okay, sorry, the beginning of the file was hidden. In this case I wonder if the plus one is necessary. Because if there is a merge commit, it would not be in the pull request

[aduh95]

Okay, sorry, the beginning of the file was hidden. In this case I wonder if the plus one is necessary. Because if there is a merge commit, it would not be in the pull request

It is necessary otherwise we dont validate the commit message of the first commit.

What kind of message does that commit have? Do we skip its validation?

Mary explains it better than me: #39121 (comment)

[github-actions]

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----------------------------------- PR info ------------------------------------
Title      tools: avoid fetch extra commits when validating commit messages (#39128)
   ⚠  Could not retrieve the email or name of the PR author's from user's GitHub profile!
Branch     aduh95:commit-msg-linter -> nodejs:master
Labels     meta
Commits    2
 - tools: avoid fetch extra commits when validating commit messages
 - fixup! tools: avoid fetch extra commits when validating commit messages
Committers 1
 - Antoine du Hamel 
PR-URL: https://github.com/nodejs/node/pull/39128
Reviewed-By: Mary Marchini 
------------------------------ Generated metadata ------------------------------
PR-URL: https://github.com/nodejs/node/pull/39128
Reviewed-By: Mary Marchini 
--------------------------------------------------------------------------------
   ⚠  Commits were pushed since the last review:
   ⚠  - tools: avoid fetch extra commits when validating commit messages
   ⚠  - fixup! tools: avoid fetch extra commits when validating commit messages
   ℹ  This PR was created on Wed, 23 Jun 2021 14:59:58 GMT
   ✔  Approvals: 1
   ✔  - Mary Marchini (@mmarchini) (TSC): https://github.com/nodejs/node/pull/39128#pullrequestreview-769672595
   ✔  Last GitHub Actions successful
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[aduh95]

Landed in b5aa08d