umpf: add new --override option to override topic commit-ish

[a3f]

In one project, umpf tags are pushed immediately, but branches are only pushed upstream once they are reviewed and cleared for merge into BSP. It's thus often the case, that developers want to use the upstream branches, except for that one branch they are currently working on.

This is not an unusual case and the tips-and-tricks lists some workarounds to achieve this. Provide a better way by allowing overriding single topic branches on the command-line.

[michaelolbrich]

Looks good for the most part. One small change, then it should be ready.

[a3f]

@michaelolbrich I am thinking of whether we might want to increase --override's scope a bit: If the topic doesn't already exist it will be appended to the list of topics, perhaps with a rename to --with, --inject or w/e. Example:

umpf tag utag --with existing-topic --with new-topic

This would make it more useful to cover two common cases I have: Someone umpf'd a release and I want to either override a single topic branch that exists or to add a single branch into the umpf. The alternative for the latter is currently cumbersome:

umpf show utag >series
git rev-parse new-topic
vi series # add topic and hashinfo
umpf tag utag --identical

[michaelolbrich]

I like the idea in general but I think we should have two separate options for this. --override and maybe --append.

[a3f]

I had changed the syntax from --override topic_orig:topic_override a few revisions ago to --override topic_orig=topic_override, because I found it clearer: When doing a git push, you do git push topic_override:topic_orig so I found that = would be an improvement.

Anyway, I forgot about that and tried to use umpf --override today and found that I broke error handling: git rev-parse returns text even if it fails, so we need to always check the exit code. I learnt that the bash syntax of

if ! rev="$(${GIT} rev-parse "${OVERRIDES[$topic]}^{}" 2> /dev/null)"; then

used elsewhere in umpf, does just that, so I force pushed this single change.

[michaelolbrich]

Almost there, just minor stuff in the help text.