From 9cc78e5d28e1fbf864db31c5f404493b5ab798fb Mon Sep 17 00:00:00 2001
From: sj <suresh@vicarasolutions.com>
Date: Tue, 18 Jun 2024 08:59:02 -0400
Subject: [PATCH 1/4] Trying to use Docker registry alias

---
 pants-plugins/macros.py | 6 ++++--
 pants.ci.toml           | 3 +++
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/pants-plugins/macros.py b/pants-plugins/macros.py
index 8d104ba..b7bf9ee 100644
--- a/pants-plugins/macros.py
+++ b/pants-plugins/macros.py
@@ -12,11 +12,13 @@ def docker_image_gha(name: str, **kwargs) -> None:
     #     **kwargs,
     # )
 
+    REPO_NAME = "dockerfiles"
+
     cache_from = kwargs.pop(
         "cache_from",
         {
             "type": "registry",
-            "ref": f"ghcr.io/robotpajamas/dockerfiles/{name}/build-cache:main",
+            "ref": f"@ghcr/{REPO_NAME}/{name}/build-cache:main",
         },
     )
     cache_to = kwargs.pop(
@@ -24,7 +26,7 @@ def docker_image_gha(name: str, **kwargs) -> None:
         {
             "type": "registry",
             "mode": "max",
-            "ref": f"ghcr.io/robotpajamas/dockerfiles/{name}/build-cache:main",
+            "ref": f"@ghcr/{REPO_NAME}/{name}/build-cache:main",
         },
     )
 
diff --git a/pants.ci.toml b/pants.ci.toml
index c65cb0f..16d425f 100644
--- a/pants.ci.toml
+++ b/pants.ci.toml
@@ -8,3 +8,6 @@ env_vars = [
   "ACTIONS_CACHE_URL",
   "ACTIONS_RUNTIME_TOKEN",
 ]
+
+[docker.registries.ghcr]
+address = "ghcr.io/robotpajamas"

From 4730937664e146041ec2967abfb2a5bc2baa6838 Mon Sep 17 00:00:00 2001
From: sj <suresh@vicarasolutions.com>
Date: Tue, 18 Jun 2024 10:16:31 -0400
Subject: [PATCH 2/4] Echo some env vars

---
 .github/workflows/pants.yml | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/.github/workflows/pants.yml b/.github/workflows/pants.yml
index 1098ff2..0de02a9 100644
--- a/.github/workflows/pants.yml
+++ b/.github/workflows/pants.yml
@@ -63,6 +63,18 @@ jobs:
           gha-cache-key: cache0-py${{ matrix.python_version }}
           named-caches-hash: ${{ hashFiles('build-support/lockfiles/*.lock') }}
 
+      - name: Emit GH env vars
+        run: |
+          echo "Event name: ${{ github.event_name }}"
+          echo "Base ref: ${{ github.base_ref }}"
+          echo "Head ref: ${{ github.head_ref }}"
+          echo "Ref: ${{ github.ref }}"
+          echo "Ref name: ${{ github.ref_name }}"
+          echo "Repo: ${{ github.repository }}"
+          echo "Owner: ${{ github.repository_owner }}"
+          echo "Actor: ${{ github.actor }}"
+          echo "Triggering Actor: ${{ github.triggering_actor }}"
+
       - name: Bootstrap Pants
         run: |
           pants --version

From 45fa51ace94d019be81d12cd41b1a17ae795fc5a Mon Sep 17 00:00:00 2001
From: sj <suresh@vicarasolutions.com>
Date: Tue, 18 Jun 2024 11:45:25 -0400
Subject: [PATCH 3/4] Testing out new cache strategy

---
 pants-plugins/macros.py | 50 ++++++++++++++++++++++++++++++++---------
 1 file changed, 39 insertions(+), 11 deletions(-)

diff --git a/pants-plugins/macros.py b/pants-plugins/macros.py
index b7bf9ee..c7ad06e 100644
--- a/pants-plugins/macros.py
+++ b/pants-plugins/macros.py
@@ -1,3 +1,39 @@
+def default_ghcr_cache(target_name: str) -> tuple[str, Optional[str]]:  # noqa: F821
+    """
+    From Github Actions default env vars, try to constitute
+    https://docs.github.com/en/actions/learn-github-actions/variables#default-environment-variables
+    """
+    # Need to specify this, because Pants doesn't reconcile `@ghcr` in the cache details
+    REGISTRY = "ghcr.io/robotpajamas"
+    REPO_NAME = "dockerfiles"
+
+    # These are always populated in a PR, but not in a direct push
+    head_ref: str = env("GITHUB_HEAD_REF", "")  # noqa: F821
+    base_ref: str = env("GITHUB_BASE_REF", "")  # noqa: F821
+
+    # This is always populated, but in a PR it is: <pr_number>/merge - if we're in a PR, ignore
+    ref_name: str = env("GITHUB_REF_NAME", "") if not head_ref else ""  # noqa: F821
+
+    cache_from_refs = [
+        f"{REGISTRY}/{REPO_NAME}/{target_name}/build-cache:{tag.replace('/', '-')}"
+        for tag in [head_ref, base_ref, ref_name, "main"]
+        if tag
+    ]
+    cache_from = [{"type": "registry", "ref": ref} for ref in cache_from_refs]
+
+    # Cache to the head_ref only in a PR, otherwise, cache to the ref_name
+    resolved_ref = head_ref or ref_name
+    cache_to = None
+    if resolved_ref:
+        cache_to = {
+            "type": "registry",
+            "mode": "max",
+            "ref": f"{REGISTRY}/{REPO_NAME}/{target_name}/build-cache:{resolved_ref.replace('/', '-')}",
+        }
+
+    return cache_from, cache_to
+
+
 def docker_image_gha(name: str, **kwargs) -> None:
     """
     A macro to create a Docker image that caches to Github Actions, by default.
@@ -12,22 +48,14 @@ def docker_image_gha(name: str, **kwargs) -> None:
     #     **kwargs,
     # )
 
-    REPO_NAME = "dockerfiles"
-
+    cache_from, cache_to = default_ghcr_cache(name)
     cache_from = kwargs.pop(
         "cache_from",
-        {
-            "type": "registry",
-            "ref": f"@ghcr/{REPO_NAME}/{name}/build-cache:main",
-        },
+        cache_from,
     )
     cache_to = kwargs.pop(
         "cache_to",
-        {
-            "type": "registry",
-            "mode": "max",
-            "ref": f"@ghcr/{REPO_NAME}/{name}/build-cache:main",
-        },
+        cache_to,
     )
 
     docker_image(  # noqa: F821

From 8a7d77f10e02734bf05462a7ed6f0aa789f4b899 Mon Sep 17 00:00:00 2001
From: sj <suresh@vicarasolutions.com>
Date: Tue, 18 Jun 2024 11:49:18 -0400
Subject: [PATCH 4/4] Previous build added new cache - checking if hit

---
 README.md | 1 +
 1 file changed, 1 insertion(+)

diff --git a/README.md b/README.md
index 63bf96d..e789601 100644
--- a/README.md
+++ b/README.md
@@ -1,5 +1,6 @@
 # Dockerfiles
 
+## Cache Strategy
 
 ## Deprecations/Removals