From: Daniel Bratell Date: Thu, 07 Mar 2013 09:49:09 GMT Subject: Re: Merging submodules - best merge-base Message-ID: In-Reply-To: <20130306181156.GA4114@sandbox-ub> Den 2013-03-06 19:12:05 skrev Heiko Voigt : > On Mon, Feb 25, 2013 at 05:44:05PM +0100, Daniel Bratell wrote: >> I can phrase this in two ways and I'll start with the short way: >> >> Why does a merge of a git submodule use as merge-base the commit that >> was >> active in the merge-base of the parent repo, rather than the merge-base >> of >> the two commits that are being merged? >> >> The long question is: >> >> A submodule change can be merged, but only if the merge is a >> "fast-forward" which I think is a fair demand, but currently it checks >> if >> it's a fast-forward from a commit that might not be very interesting >> anymore. >> >> If two branches A and B split at a point when they used submodule commit >> S1 (based on S), and both then switched to S2 (also based on S) and B >> then >> switched to S21, then it's today not possible to merge B into A, despite >> S21 being a descendant of S2 and you get a conflict and this warning: >> >> warning: Failed to merge submodule S (commits don't follow merge-base) >> >> (attempt at ASCII gfx: >> >> Submodule tree: >> >> S ---- S1 >> \ >> \ - S2 -- S21 >> >> Main tree: >> >> A' (uses S1) --- A (uses S2) >> \ >> \ --- B' (uses S2) -- B (uses S21) >> >> >> I would like it to end up as: >> >> A' (uses S1) --- A (uses S2) ------------ A+ (uses S21) >> \ / >> \ --- B' (uses S2) -- B (uses S21)- / >> >> And that should be legal since S21 is a descendant of S2. > > So to summarize what you are requesting: You want a submodule merge be > two way in the view of the superproject and calculate the merge base > in the submodule from the two commits that are going to be merged? > > It currently sounds logical but I have to think about it further and > whether that might break other use cases. Maybe both could be legal even. The current code can't be all wrong, and this case also seems to be straightforward. /Daniel