Make migration PR commit messages configurable

[f-maier]

Tell us more.

Currently I'm facing the problem that renovate uses a hard-coded message for config migration commits which doesn't match our regex for validating commit messages. It would be much nicer if the commit message would be configurable like so:

...
"configMigration": {
    "enabled": true,
    "commitMessageLowerCase":"never",
    "commitMessageAction": "Migrate",
    ...
  },
...

[aschleifer]

It would also be ok if the commit message fore config updates would adhere to semanticCommit* variables if they are configured. We do override the semanticCommitScope for one of our repos, but the config upgrade still is a chore(config) which is invalid in this repository.

[aschleifer]

Also it seems the labels configuration is not applied for migrateion MRs.

[jamietanna]

Thanks for raising - we'll look at handling this as part of #40124 / as a separate Issue