PR: Update remote when syncing subrepos

[mrclary]

When updating subrepos in Spyder using the current instructions (git subrepo clone), the remote specification in .gitrepo is not updated to reflect the cloned remote, but remains as the original upstream specification.

This can be an issue for any process that requires access to the remote repository at the commit and/or branch specified in .gitrepo, since that commit and/or branch may not exist on the (incorrectly) specified remote. The conda-based installers are an example of such a process.

This PR changes the instructions to use git subrepo pull ... -r <remote> -u to ensure that the remote specification is also updated.

Affirmation

By submitting this Pull Request or typing my (user)name below,
I affirm the Developer Certificate of Origin
with respect to all commits and content included in this PR,
and understand I am releasing the same under Spyder's MIT (Expat) license.

I certify the above statement is true and correct: @mrclary

[ccordoba12]

A couple of comments:

• What does -u do?
• I tried to use gitsubrepo pull before instead of clone, but I think it doesn't work to update a subrepo here if your PR there was rebased (because the old parent commit is different after the rebase). Did you test that possibility?

[mrclary]

• What does -u do?

    -u, --update          Add the --branch and/or --remote overrides to .gitrepo

• I tried to use gitsubrepo pull before instead of clone, but I think it doesn't work to update a subrepo here if your PR there was rebased (because the old parent commit is different after the rebase). Did you test that possibility?

Ahh, good point. I did not test that, but I'll be sure to do so.
We currently use the -f (force) flag, and it will persist with this PR. I'll check to see if that has any effect. Also, there is a -M (method) flag that can take values 'merge' or 'rebase'; 'merge' is the default. I will check to see whether this has any effect as well.

[mrclary]

Okay, upon testing, I can confirm the following for git subrepo pull on a remote rebase:

• Without -f (force), an error is raised because the previous commit no longer exists (no fast-forward merge is possible). This reproduces the condition that @ccordoba12 was concerned about.
• Using -M rebase (method) has no effect.
• With -f (force), the subrepo is successfully updated.

So, I think we should be good.

[CAM-Gerlach]

As this PR seems focused on just updating the git-subrepo commands, and my experience with using git-subrepo pales next to @ccordoba12 and @dalthviz (whereas I do make much heavier use of git submodule), I'll leave the review in their much more capable hands

[ccordoba12]

Okay, upon testing, I can confirm the following for git subrepo pull on a remote rebase ...
So, I think we should be good.

Great! Thanks for checking that @mrclary!

[ccordoba12]

Thanks @mrclary!

[dalthviz]

Thanks @mrclary ! LGTM 👍