Allow the merge target to be changed or ignored

[justinrobots]

Problem

Currently, GL makes a best-guess on what the merge target for the current branch is, but users don't have a way to ignore or change this if it is not correct.

Solution

Preserve the assumed merge target and add a new field to capture a user-defined merge target.

Put a button to edit the merge branch here:

Also it would be nice if we could signal to users when we’re showing an assumed merge target, with an option to ignore / set their own. Need to explore more how that could be shown without adding too much noise. Probably, we could modify the ? tooltip based on which merge target is being displayed (the assumed one vs. the user-defined one) to be clear about which is being shown. Maybe that icon even changes from a ? to something that indicates it’s a user-defined target when that is the case. On a daily-meeting we decided that we don't need it.

Follow-ups:

• start using merge-target in "Create a PR" action (create an issue for it. discussed in slack)

Verification steps

• check that user can set a merge-target to another branch (using the pencil icon on Home)
  • see the result in the tooltip on Home
  • see the result in .git/config
• check that user can reset a merge-target back to the detected branch:
  • see the result in the tooltip on Home
  • see the result in .git/config
• check that user can set and reset a merge target by pallet command directly:
  • check that "back" button works
• make sure that an issue for the item from the "Follow-ups" section has been created : )

[sergeibbb]

@justinrobots @eamodio

1. Is it related to the "create a PR" feature or something else, or both?
2. If "yes" does it mean that a new step in the flow appears? Where, for example, we ask user about a target branch with having the guessed branch selected by default, or something else?
3. "Preserve the assumed merge target": in order to do... what? Will user see this value somehow?

[sergeibbb]

questions above have been discussed on the daily meeting. Answers:

1. No. It's related the "Merge Target" on the Home Screen.

2. "no" ---

3. "Preserve the assumed merge target": in order to do reset the user's choice to what we detected earlier.

cc @justinrobots , @eamodio

[sergeibbb]

@justinrobots

Here is some intermediate result:

---

Now I'm working on showing whether we show an auto-detected merge base or user defined:

and add an ability to reset user's choice, probably something like this:

cc @d13