ms3 v2.3.0 can be used as pre-commit hook

What's Changed

• Adds 'ms3 precommit' and makes the repo usable as a hook by @johentsch in #106
  • The new ms3 precommit command is simply a wrapper around ms3 review that accepts the --files arguments as positional arguments. This is required for the command to be useable as an entry point for a Git pre-commit, which passes the paths of modified or added files as positional arguments. In addition, the command executes git add -A after the review so that all changed files are included.
  • This is to work in the first version of the new, localized, DCML annotation workflow that runs on the annotator's machine before committing, rather than on a GitHub runner after pushing. Things that might be changed in the future:
    • The ms3 precommit command could convert the positional arguments into a regular expression to be passed to -i/--include instead of using the deprecated --files.
    • At some point a mechanism might be needed that makes it possible for the hook to ignore warnings that were already there, i.e., which are not caused/added by the current commit. Currently one would have to remove --fail from the repo's args configuration but that would let all warnings pass and would be besides the point.
  • New method score.mscx.update_metadata() to facilitate (manual) updating of the key-value pairs.
  • Comparison files come with the metadata key compared_against=<commit hash> when the comparison has been performed against a particular git revision.
  • "LATEST_VERSION" is now accepted as argument to git_revision and resolves to the latest version tag (falling back to the current HEAD if the repo has no tags)
• Extended excerpting functionality by @leobruneau in #105
  • It is now possible to replace head and tail of an excerpt with rests. This does not look pretty but it is an easy way to create audio excerpts starting and ending at the given points in time.
  • It is now possible to set an arbitrary tempo by inserting an invisible metronome mark at the beginning of excerpts.
  • score.mscx.store_phrase_excerpts() makes use of this to omit notes before and after the actual phrase
  • new methods accessible via score.mscx:
    • store_measures()
    • store_within_phrase_excerpts()
    • store_phrase_endings()
    • store_random_excerpts()

Full Changelog: v2.2.2...v2.3.0