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Diffstat (limited to 'Documentation/howto/revert-a-faulty-merge.txt')
| -rw-r--r-- | Documentation/howto/revert-a-faulty-merge.txt | 34 |
1 files changed, 19 insertions, 15 deletions
diff --git a/Documentation/howto/revert-a-faulty-merge.txt b/Documentation/howto/revert-a-faulty-merge.txt index 6fd711996a..19f59cc888 100644 --- a/Documentation/howto/revert-a-faulty-merge.txt +++ b/Documentation/howto/revert-a-faulty-merge.txt @@ -7,6 +7,10 @@ Abstract: Sometimes a branch that was already merged to the mainline after the offending branch is fixed. Message-ID: <7vocz8a6zk.fsf@gitster.siamese.dyndns.org> References: <alpine.LFD.2.00.0812181949450.14014@localhost.localdomain> +Content-type: text/asciidoc + +How to revert a faulty merge +============================ Alan <alan@clueserver.org> said: @@ -26,14 +30,14 @@ The history immediately after the "revert of the merge" would look like this: ---o---o---o---M---x---x---W - / + / ---A---B where A and B are on the side development that was not so good, M is the merge that brings these premature changes into the mainline, x are changes unrelated to what the side branch did and already made on the mainline, and W is the "revert of the merge M" (doesn't W look M upside down?). -IOW, "diff W^..W" is similar to "diff -R M^..M". +IOW, `"diff W^..W"` is similar to `"diff -R M^..M"`. Such a "revert" of a merge can be made with: @@ -43,14 +47,14 @@ After the developers of the side branch fix their mistakes, the history may look like this: ---o---o---o---M---x---x---W---x - / + / ---A---B-------------------C---D where C and D are to fix what was broken in A and B, and you may already have some other changes on the mainline after W. If you merge the updated side branch (with D at its tip), none of the -changes made in A nor B will be in the result, because they were reverted +changes made in A or B will be in the result, because they were reverted by W. That is what Alan saw. Linus explains the situation: @@ -77,7 +81,7 @@ In such a situation, you would want to first revert the previous revert, which would make the history look like this: ---o---o---o---M---x---x---W---x---Y - / + / ---A---B-------------------C---D where Y is the revert of W. Such a "revert of the revert" can be done @@ -86,17 +90,17 @@ with: $ git revert W This history would (ignoring possible conflicts between what W and W..Y -changed) be equivalent to not having W nor Y at all in the history: +changed) be equivalent to not having W or Y at all in the history: ---o---o---o---M---x---x-------x---- - / + / ---A---B-------------------C---D and merging the side branch again will not have conflict arising from an earlier revert and revert of the revert. ---o---o---o---M---x---x-------x-------* - / / + / / ---A---B-------------------C---D Of course the changes made in C and D still can conflict with what was @@ -107,25 +111,25 @@ faulty A and B, and redone the changes on top of the updated mainline after the revert, the history would have looked like this: ---o---o---o---M---x---x---W---x---x - / \ + / \ ---A---B A'--B'--C' If you reverted the revert in such a case as in the previous example: ---o---o---o---M---x---x---W---x---x---Y---* - / \ / + / \ / ---A---B A'--B'--C' where Y is the revert of W, A' and B' are rerolled A and B, and there may -also be a further fix-up C' on the side branch. "diff Y^..Y" is similar -to "diff -R W^..W" (which in turn means it is similar to "diff M^..M"), -and "diff A'^..C'" by definition would be similar but different from that, +also be a further fix-up C' on the side branch. `"diff Y^..Y"` is similar +to `"diff -R W^..W"` (which in turn means it is similar to `"diff M^..M"`), +and `"diff A'^..C'"` by definition would be similar but different from that, because it is a rerolled series of the earlier change. There will be a lot of overlapping changes that result in conflicts. So do not do "revert of revert" blindly without thinking.. ---o---o---o---M---x---x---W---x---x - / \ + / \ ---A---B A'--B'--C' In the history with rebased side branch, W (and M) are behind the merge @@ -160,7 +164,7 @@ merged. So it's debugging hell, because now you don't have lots of small changes that you can try to pinpoint which _part_ of it changes. But does it all work? Sure it does. You can revert a merge, and from a -purely technical angle, git did it very naturally and had no real +purely technical angle, Git did it very naturally and had no real troubles. It just considered it a change from "state before merge" to "state after merge", and that was it. Nothing complicated, nothing odd, nothing really dangerous. Git will do it without even thinking about it. |