How does the 3 way merge in Mercurial/Meld work?
I'm working on a project where I have a commit that introduced a feature with major problems that weren't discovered immediately. Now I want to completely remove that revision while keeping the work following it but i'm having a hard time wrapping my head around this 3 way merge. Here is a simplified graph of my project.
o changeset: 134:7f81764aa03a | tag: tip | parent: 128:451d8a19edea | summary: Backed out changeset 451d8a19edea | | @ changeset: 133:5eefa40e2a29 | | summary: (Change I need to keep keep) | | *snip 3 commits* | o changeset: 129:5f6182a97d40 |/ summary: (Change I need to keep keep) | o changeset: 128:451d8a19edea | summary: (Change that introduced a major problem) | o changeset: 127:4f26dc55455d | summary: (summary doesn't matter for this question)
If I understand this correctly, r127 and r134 are exactly the same. When I hg up -C -r 133 and then run hg merge, Meld pops up with three forms of one of my files: local, base, and other. local seems to be r133 but i'm having a hard time wrapping my head around what "base" and "other" mean.
Answer
Local is r133
Other is r134
Base is r128 (the common ancestor to both r133 and r 134)
When you perform a 3 way merge it compares all three of those together to help you decide what to take and from where. By seeing what change is in the other revision and what the common ancestor looked like you are able to make a much more informed decision about what to keep and what to change.