Subject: Re: [PATCH v2 1/2] CI: limit GitHub Actions to designated branches

From: Đoàn Trần Công Danh <[email-masked]>
Date: Wed, 6 May 2020 07:46:12 +0700

On 2020-05-05 17:04:51-0400, Jeff King <[email-masked]> wrote:
> We could likewise try to get some information from the branch name. But
> that leads to debates about whether the default should be "off" or "on",
> and overriding still ends up somewhat awkward. If we default to "on",
> you have to remember to name your branches appropriately to skip CI. And
> if "off", you end up having to contort your branch names or duplicate
> your pushes with an extra refspec.
> 
> By comparison, this commit's solution lets you specify your config once
> and forget about it, and all of the data is off in its own ref, where it
> can be changed by individual forks without touching the main tree.

How about supports the best of both worlds.

Let's say support wildcard 'wip/**' for opt-out.
And use "./allow-ref" to filter everything that passed the wildcard.

> I used refs/ci/config as the config ref, which should be a commit whose
> tree contains various config files (right now the only one is
> "ref-whitelist"). It was intentional to avoid refs/heads/ here so we
> don't conflict with any branch workflows. But it does make it a little
> awkward to edit, since you can't check it out directly.
> 
> Right now the logic is to run CI for all branches by default, unless a
> whitelist exists, in which case the branch must be mentioned there
> (using its fully qualified ref name). We could easily add in a
> blacklist, as well. Or since we're running a shell in a VM, we really
> could just run "./allow-ref $refname" and let individual forks specify
> whatever shell code they like.

Should we go with this route, here is a fix-up patch for your,
(after cherry-pick my [1/3])
--------------------8<-------------------
Subject: [PATCH] fixup! ci: allow per-branch config for GitHub Actions

Signed-off-by: Đoàn Trần Công Danh <[email-masked]>
---
 .github/workflows/main.yml      |  3 +--
 Documentation/SubmittingPatches | 12 ++++++++++++
 contrib/ci-config-allow-ref     |  9 +++++++++
 3 files changed, 22 insertions(+), 2 deletions(-)
 create mode 100755 contrib/ci-config-allow-ref

diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index 51f4ff6e89..08217c5ed8 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -19,8 +19,7 @@ jobs:
           name: check whether CI is enabled for ref
           run: |
             enabled=yes
-            if test -e ref-whitelist &&
-               ! grep '^${{ github.ref }}$' ref-whitelist
+            if test -x allow-ref && ! ./allow-ref '${{ github.ref }}'
             then
               enabled=no
             fi
diff --git a/Documentation/SubmittingPatches b/Documentation/SubmittingPatches
index 8686318550..8175424929 100644
--- a/Documentation/SubmittingPatches
+++ b/Documentation/SubmittingPatches
@@ -82,6 +82,18 @@ Alternately, you can use GitHub Actions (which supports testing your changes
 on Linux, macOS, and Windows) by pushing into a branch in your fork
 or opening a GitHub's Pull Request against
 https://github.com/git/git.git or a fork of that repository.
+In the event that you only want to trigger GitHub Actions for specific
+refname, you can create an executable file named `allow-ref` in
+`refs/ci/config`. Those below steps may help you:
+--------------
+$ git checkout --orphan ci-config
+$ cp contrib/ci-config-allow-ref allow-ref
+$ $EDITOR allow-ref
+$ git rm -rf .
+$ git commit allow-ref
+$ git push <your-fork> HEAD:refs/ci/config
+--------------
+
 
 Do not forget to update the documentation to describe the updated
 behavior and make sure that the resulting documentation set formats
diff --git a/contrib/ci-config-allow-ref b/contrib/ci-config-allow-ref
new file mode 100755
index 0000000000..b53e9ddbd0
--- /dev/null
+++ b/contrib/ci-config-allow-ref
@@ -0,0 +1,9 @@
+#!/bin/sh
+# Sample filter for GitHub Actions
+# GitHub Actions will run if and only if this script exit with zero status
+
+REFNAME="$1"
+
+case "$REFNAME" in
+refs/heads/no-ci*) exit 1 ;;
+esac
-- 
2.26.2.672.g232c24e857