Streamline usable as a "tool" for an arbitrary repo/PR

[yarikoptic]

Somewhat relates to #162 as that one to expose API to fetch logs for specific commit (PR).

While working on a feedstock repo, I realized that what I would have loved to be able to just request all logs for my now failed PR. Establishing config etc is like asking to duplicate data given my current situation -- all of it might be deduced

• I am in a feature branch which has default remote associated so I can get github URL, know the branch

• from that remote I can figure either it is a fork - if fork, get upstream github repo

• discover PR on upstream repo which has my PR/commit

• fetch all the logs for which I find CI having ran anything

• I might not be able or want to modify the repo with tinuous configuration file.

• I would not care much about paths, i.e. some sensible default would be good enough

Idea:

If no config file given:

• if tinuous doesn't find tinuous.yaml can assume .git/tinuous/config.yaml to be the default location (.git/ is autodiscovered for a repo) if no config file is provided

• tinuous bootstrap-config command would discover relevant details and create config in the specified on CLI or the default (above) location

• add tinuous fetch-current-pr command (so interface to re-fetch logs for some specific PR #162 is relevant).

Then in any given repo I could just tinuous bootstrap-config && tinuous fetch-current-pr to get a copy of all the logs for the PR and investigate them without establishing "full blown" archive of logs like we do for our tools. Any other time in any other PR later on I could just tinuous fetch-current-pr and get a copy of relevant logs

WDYT @jwodder ?

[yarikoptic]

ping on this one, I kept wishing I had tinuous fetch-current-pr or even some bot to just ask @tinuous-bot fetch this PR which would have populated logs in some repo of mine for a given project/PR.