Sheriffing/How To/Merges

Goal

Each sheriff should perform a merge at the beginning of their work day. Effectively, this results in two sets of merges every day to/from autoland and mozilla-inbound to mozilla-central

Choosing a changeset to merge

For merges from the integration trees to mozilla-central, you should choose a changeset with a green PGO run to avoid bustages on nightly builds that also run PGO. You need to also make sure that are *NOT* any backouts *after* that changeset.

Order of operations

Integration branches should be merged to mozilla-central first, then mozilla-central should be merged back to the integration branches. These merge instructions were copied from Sheriffing From Unified Repos document.

Merging from autoland and mozilla-inbound to mozilla-central

Example mozilla-inbound to mozilla-central merge:

cd mozilla-unified
hg pull 
hg update central
hg merge -r <changeset> # the green changeset with PGO runs on mozilla-inbound
hg commit -m "Merge inbound to mozilla-central"
hg push -r . central

After you, be sure to use Bugherder to classify any failures on your merge commit. It's available from the menu for the push on Treeherder

Merging back from mozilla-central to autoland and mozilla-inbound

Example mozilla-central to mozilla-inbound merge:

cd mozilla-unified
hg pull
hg update inbound
hg merge central
hg commit -m "Merge mozilla-central to mozilla-inbound"
hg push -r . inbound 

These commands *might* result in race conditions on the tree when it is busy. Under those circumstances, this commands avoid delays between steps:

cd mozilla-unified
hg pull && hg update inbound && hg merge central && hg commit -m "Merge mozilla-central to mozilla-inbound" && hg push -r . inbound

When there is nothing to merge

You run hg update to get a working copy information, but there are no changes on mozilla-central and so nothing to merge. The workflow for this case is:

1. Run hg update
   • You can run hg out to list all the changesets to merged to mozilla-central.
2. Because there's been no merge, you won't have a commit containing a approval message, e.g. "merge a to b a=me." This means you will run afoul of the hg hook telling you that the m-c repo is set to approval-only. You need to temporarily set the mozilla-central tree to "open" via Treestatus to be able to push.
3. Push your changes from Step 1.
4. Set the m-c tree back to "approval-required" in Treestatus. This is important because if we miss this, we risk unexpected pushes to mozilla-central since some people might think the open tree is intentional.
5. Use Bugherder to mark and failures as usual for your push.
6. Now when you merge from mozilla-inbound you get the note that you need to merge.