Jacob Keller <jacob.keller@xxxxxxxxx> writes: > I think both questions are valuable, the first is "which commit last > had this blob", the second is "which commit first introduced this > blob", neither of which can always give a definitive answer. It really > depends on what question you're asking up front. Given that "describe" is about giving an object _a_ name that is plausibly useful to refer to it, it is not a good match for the above query that wants to know where it came from, how long it remains in the tree and where it ceases to be relevant. In order to support that use case, a totally different and possibly more useful avenue would be to think how this can be hooked into "git log" machinery. A refresher for how "git log [--options] <pathspec>" works may be beneficial. We walk history and compare the tree of the commit we are looking at with the tree of its parent commits. If everything within <pathspec> is the same, we mark the transition between the parent and our commit TREESAME (other commits, i.e. the ones that have meaningful change within <pathspec>, are !TREESAME). Then the output routine presents the set of commits that includes commits that are !TREESAME, within the constraints of the --options given (e.g. with --full-history, sides of a merge that is TREESAME may still be shown to preserve connectedness of the resulting graph). It is easy to imagine that we can restrict "git log" traversal with a "--blobchange=<blob>" option instead of (or in addition to) the limitation <pathspec> gives us. Instead of treating a commit whose diff against its parent commit has any filepair that is different within <pathspec> as "!TREESAME", we can treat a commit whose diff against its parent commit has a filepair that has the <blob> on either side of the filepair as "!TREESAME" (in other words, we ignore a transition that is not about introducing or forgetting the <blob> we are looking for as an "interesting change"). That would give you a commit history graph in which only (and all) such commits that either adds or removes the <blob> in it. Hmm?
