Bug 1905941 - Merge automation workaround for comm-central-to-beta and .gecko_rev.yml. r=dandarnell

This should be fixed by adding functionality to deal with .gecko_rev.yml to
Treescript. However in the interest of getting merge automation working add
this workaround.
There's no GECKO_HEAD_REV field in .gecko_rev.yml when comm-central-to-beta
runs, so instead create a line that can be easily replaced with the correct
data.

Differential Revision: https://phabricator.services.mozilla.com/D221194

--HG--
extra : rebase_source : 9926068cbee7017d06a91296926d041fd3dfe6f9
extra : amend_source : f8b057b344b9f7e76dc56ab84b5d69527b2fa3d9
extra : absorb_source : be4bdd4c1dd27c18cf48248768e225a5a0a14301

.gecko_rev.yml

@@ -2,6 +2,7 @@
 GECKO_BASE_REPOSITORY: https://hg.mozilla.org/mozilla-unified
 GECKO_HEAD_REPOSITORY: https://hg.mozilla.org/mozilla-central
 GECKO_HEAD_REF: default
+######
 
 ### For comm-central
 # GECKO_BASE_REPOSITORY: https://hg.mozilla.org/mozilla-unified

taskcluster/comm_taskgraph/transforms/merge_automation.py

@@ -92,6 +92,7 @@ def get_gecko_rev_yml(repo_base_url):
 
 
 def get_upstream_tag(tag_regex, base_regex, repo):
+    print(f"get_upstream_tag: Looking for {tag_regex} or {base_regex}")
     base_tag_matcher = re.compile(base_regex)
     release_tag_matcher = re.compile(tag_regex)
 
@@ -140,6 +141,8 @@ def pin_gecko_rev_yml(config, tasks):
         if "merge_config" not in config.params:
             break
 
+        behavior = config.params["merge_config"]["behavior"]
+
         resolve_keyed_by(
             task,
             "worker.gecko-rev",
@@ -147,7 +150,7 @@ def pin_gecko_rev_yml(config, tasks):
             **{
                 "project": config.params["project"],
                 "release-type": config.params["release_type"],
-                "behavior": config.params["merge_config"]["behavior"],
+                "behavior": behavior,
             },
         )
 
@@ -183,11 +186,16 @@ def pin_gecko_rev_yml(config, tasks):
                     "GECKO_HEAD_REF", gecko_rev_yml["GECKO_HEAD_REF"], tag_data["tag"]
                 )
             )
-            replacements.extend(
-                mk_gecko_rev_replacement(
-                    "GECKO_HEAD_REV", gecko_rev_yml["GECKO_HEAD_REV"], tag_data["node"]
+            if behavior == "comm-central-to-beta":
+                replacements.append(
+                    [".gecko_rev.yml", "######", f"GECKO_HEAD_REV: {tag_data['node']}"]
+                )
+            else:
+                replacements.extend(
+                    mk_gecko_rev_replacement(
+                        "GECKO_HEAD_REV", gecko_rev_yml["GECKO_HEAD_REV"], tag_data["node"]
+                    )
                 )
-            )
 
             merge_config["replacements"].extend(replacements)
 

taskcluster/kinds/merge-automation/kind.yml

@@ -78,5 +78,6 @@ tasks:
                         upstream: mozilla-esr128
                         tag: 'FIREFOX_{major_version}_{minor_version_plus1}(_\d+)?esr_BUILD\d'
                         base: '(FIREFOX_ESR_{major_version}_BASE|FIREFOX_{major_version}_{minor_version}(_\d+)?)esr_BUILD\d'
+                    default: null
         run-on-projects: []
         expiration-policy: long