try-branches

name	try-branches
description	Push a commit to try on multiple Firefox branches (beta, release, ESR). Use when testing if a patch builds/works on older Firefox versions for uplift.
argument-hint	<commit> <branch1> [branch2] ...
context	fork

Try Branches

Push a commit to the try server on multiple Firefox branches using the Lando API directly. This is useful for testing uplift compatibility on beta, release, and ESR branches.

Arguments

$ARGUMENTS should be: <commit-hash> <branch1> [branch2] ...

Where branches can be: beta, release, esr115, esr128, esr140, or any branch name available under upstream/ remote (which should point to https://github.com/mozilla-firefox/firefox.git).

Example: /try-branches HEAD beta release esr128 esr115

Process

1. Parse the commit hash and target branches from arguments
2. Ensure upstream remote exists pointing to https://github.com/mozilla-firefox/firefox.git
3. Fetch the target branches from upstream if not already fetched
4. For each target branch: a. Create a temporary local branch try-<branch> from upstream/<branch> b. Cherry-pick the commit onto it c. If there are conflicts, resolve them and inform the user about the resolution d. Generate a git format-patch of the cherry-picked commit e. Push to try via the Lando API
5. Generate patch files in the repo root for any branches that required conflict resolution
6. Switch back to the original branch
7. Print a summary table with Treeherder links

Cherry-pick conflict handling

If a cherry-pick has conflicts:

• Try to resolve them automatically if possible
• If auto-resolution fails, abort, inform the user, and skip that branch
• For branches with resolved conflicts, generate a .patch file at the repo root (e.g., esr115.patch)

Lando API push method

Use a Python script to call the Lando API directly. This avoids issues with mach try on older branches that lack Lando support or have incompatible git-cinnabar requirements.

The script should:

1. Read the auth token from ~/.mozbuild/lando_auth0_user_token.json
2. Generate the patch with git format-patch -1 <commit> --stdout
3. Generate the correct try_task_config.json as a second patch:

   {
       "parameters": {
           "filters": ["try_auto"],
           "optimize_strategies": "gecko_taskgraph.optimize:tryselect.bugbug_reduced_manifests_config_selection_medium",
           "optimize_target_tasks": true,
           "test_manifest_loader": "bugbug",
           "try_mode": "try_auto",
           "try_task_config": {}
       },
       "version": 2
   }
   

4. POST to https://api.lando.services.mozilla.com/try/patches with:

   {
       "base_commit": "<upstream branch tip git SHA>",
       "base_commit_vcs": "git",
       "patch_format": "git-format-patch",
       "patches": ["<base64 commit patch>", "<base64 try_task_config patch>"]
   }
   

5. The try_task_config patch should be a valid git format-patch style patch that creates try_task_config.json

Auth token

If the auth token at ~/.mozbuild/lando_auth0_user_token.json doesn't exist or is expired, tell the user to run ./mach try auto on any branch first to authenticate, which will cache the token.

Important notes

• Always switch back to the user's original branch when done
• Clean up any temporary state (stashed changes, staged files)
• The try-<branch> local branches are left around for reference but can be deleted
• If a branch already has a try-<branch> local branch, delete and recreate it