cmd/dist: use jj as a fallback when there's no VERSION file and we're not in a git repo

[matloob]

When there's no VERSION file, dist will try to synthesize a devel version using the git commit hash and timestamp. We should also support people developing go without a git-backed jj repo by falling back to using jj if there's no VERSION file and no git repo.

[gopherbot]

Change https://go.dev/cl/759320 mentions this issue: cmd/dist: try to use jj commit info for devel version

[matloob]

Update: as pointed out by @prattmic jj by default creates a colocated git repo. I think this would be useful primarily when creating additional jj workspaces.

[gabyhelp]

Related Code Changes

• cmd/dist: try to use jj commit info for devel version

_{(Emoji vote if this was helpful or unhelpful; more detailed feedback welcome in this discussion.)}

[gopherbot]

Change https://go.dev/cl/821320 mentions this issue: cmd/dist: don't mistake a missing VCS tool for a repo