Sergio schrieb: > 1) Grafts and replace entries seem to operate on different aspects of the > history graph. Grafts operate on arcs and replace on nodes. Correct, but see below about tree and blob objects. > As such, replace entries seem less general to me. With grafts you can only change parenthood; with replace entries you can change parenthood *and* all other aspects of a commit (message, author, committer, dates). Hence, replace entries are more general than grafts. > Apparently, to simulate a graft with replace entries, you need to introduce > extra commit objects. For instance, if object B has no parents, to pretend that > it derives from some A, one needs to create an object B' equivalent to B but > for the parents and then replace B by B', is this right? Yes. Use git-cat-file + edit + git-hash-object as explained in this message just the other day: http://thread.gmane.org/gmane.comp.version-control.git/129727/focus=129907 > Conversely, I guess > you can always simulate a replace entry with the graft mechanism, without the > need to add any extra commit object. Am I overlooking something? You cannot; see above. You can even replace tree objects and blob objects using replace entries, IIUC, but you cannot do that with grafts. > 2) Is it currently possible to use a replace entry to replace a commit object > with nothing? Namely if B has A as its sole parent, is it possible to have a > replace entry such as A-sha1 becomes null, to pretend that B is a hierarchy > root? Sure. Just make a commit object that does not have parents. > 3) If I remember correctly, there was a reason why grafts were not considered > suitable for transferring across repos. Can someone remind me about it? How > does the replace mechanism address this issue? The problem with grafts was that, for example, git-pack-objects obeyed the graft, and could create a broken repository by removing grafted-away objects. And since git-fsck also obeyed the graft, it did not notice the breakage. OTOH, history walkers (upload-pack, send-pack, pack-objects) and fsck never obey replace entries in the history. But they do keep track of them (and the history that they reference) because they are referenced from the refs/replace namespace. -- Hannes -- To unsubscribe from this list: send the line "unsubscribe git" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html