github: Add action for automated issue notification

[tstellar]

Summary

This adds a github action that will mention a team called issue-subscribers-$LABEL
whenever a label is added to a bug. Mentioning the team will automatically
subscribe all team members to the bug.

[asl]

@tstellar Does it work for our "complex" labels? E.g. "lld:ELF" or "tools:llvm-ar/llvm-ranlib"?

[probinson]

Presumably we can generate the team memberships from the Bugzilla component auto-subscribers easily enough, even if it's manual.
I take it we'd need one of these sub-teams per label (mostly); is there a max number of teams?

(I don't know anything about GH actions, this is responding to the high-level description not the implementation.)

[tstellar]

Add support for labels with colons in name.

[tstellar]

Rename script to issue-subscriber.
Add support for labels with /.

[tstellar]

In D114412#3189499, @asl wrote:

@tstellar Does it work for our "complex" labels? E.g. "lld:ELF" or "tools:llvm-ar/llvm-ranlib"?

I updated the patch to handle these cases.

[tstellar]

In D114412#3189533, @probinson wrote:

Presumably we can generate the team memberships from the Bugzilla component auto-subscribers easily enough, even if it's manual.

Yes, we can do that.

I take it we'd need one of these sub-teams per label (mostly); is there a max number of teams?

I'm not aware of a limit on the number of teams.

(I don't know anything about GH actions, this is responding to the high-level description not the implementation.)

[keith]

In D114412#3189533, @probinson wrote:

I take it we'd need one of these sub-teams per label (mostly); is there a max number of teams?

For reference I am in a github org with ~6k teams without issue.

[alexbatashev]

.github/workflows/issue-subscriber.yml

12

Could you please apply fix from https://reviews.llvm.org/D115708 here as well?

[tstellar]

Disable action for forks.

[alexbatashev]

Thanks a lot, @tstellar!

[kristof.beyls]

I think this would be useful to have, as writing fine-grained filter rules is not necessarily easy or even doable in some mail clients, such as gmail.
With that in mind, I wonder if this action (which if I understand correctly will add a comment mentioning "@issue-subscribers-label"), results in the corresponding notification email adding "[e-mail]"? I hope it does as that probably would make it easier to write email filters.

The only other thought I have here is if any other github projects have similar notification issues and if there is a de facto standard amongst such project on how to solve that?

[mehdi_amini]

Ping on this issue? We're really missing on the auto-subscribe that Bugzilla was offering :(

.github/workflows/issue-subscriber.yml

+name: Issue Subscriber
+
+on:
+  issues:
+    types:
+      - labeled
+
+jobs:
+  auto-subscribe:
+    runs-on: ubuntu-latest
+    if: github.repository == 'llvm/llvm-project'
+    steps:
+    - name: Update watchers
+      uses: actions/github-script@v5
+      with:
+        github-token: ${{ secrets.ISSUE_MENTION_SECRET }}
+        script: |
+            const teamname = "issue-subscribers-" + context.payload.label.name.replace(/ /g, "-").replace(":","-").replace("/","-");
+            const comment = "@llvm/" + teamname;
+            try {
+              // This will throw an exception if the team does not exist and no
+              // comment will be created.
+              team = await github.rest.teams.getByName({
+                org: context.repo.owner,
+                team_slug: teamname
+              });
+              github.rest.issues.createComment({
+                issue_number: context.issue.number,
+                owner: context.repo.owner,
+                repo: context.repo.repo,
+                body: comment
+              });
+            } catch (e){
+              console.log(e);
+            }