How can I do a changeset based merge instead of file-by-file based merge with Mercurial?

Question

When performing a merge with Mercurial, it wants to merge conflicting files one at a time which just isn't a productive workflow on large merge sets. Instead, what I would like to do is merge the entire changesets of both heads (like using kdiff3 to diff 2 heads). To me that sounds straightforward but I can't figure out how to achieve it.

So far, the closest I can get is to go through the merge the usual way, leave all the conflicts unresolved (a file at a time...), and then hg vdiff -rHead1 -rHead2 - but vdiff (using kdiff3) doesn't seem to have options for passing the tool an output dir (the current working dir) and instead launches with the output dir as a tempdir (possibly -o is the answer?).

Let me put it another way - I want to use kdiff to merge two heads into my working directory. I want the results in my working dir to be my merge that I can commit.

I must be missing something obvious, I can't be the only one who wants to do this.

Answer 1

I came up with a solution that achieves what I want but I still feel like it's a kludge.

• Start with an empty working dir with 2 heads: Mine and Theirs.
• Update working dir to Mine:
  hg update [My head's rev here]
• Perform a merge, but fail all files that Merc can't handle automatically without launching a merge tool and keep "My" files when in conflict:
  hg --config "ui.merge=internal:fail" merge

See https://www.mercurial-scm.org/wiki/TipsAndTricks#head-9f405488b6d3b3d092a09aafa28db515ba44c742 for how-to merge/fail details.

Now I've got a working dir with as much as auto could figure out, but any outstanding files still untouched from Mine. (Use hg resolve -l to see the Mercurial's resolution status of current files)

• Now I can vdiff my working dir against the Theirs head which gives me the high level, changeset-to-changeset merge that I was looking for.

hg vdiff -r [Theirs head's rev here]

Note: If you're using WinMerge for your vdiffs , then make sure it has an /r switch as an option which will do a subdirectory compare and - if WinMerge config is set to use Tree-View - will give a great tree comparison. From Mercurial.ini:

[extdiff]
cmd.vdiff = C:\Program Files\WinMerge\WinMergeU.exe
opts.vdiff = /e /ub /r /dl other /dr local
Now I can work the entire directory which includes the unresolved files and make project wide changes as necessary (ie. maybe resolving one file requires additional changes in another).

• When done use resolve to mark all files resolved for Merc and then commit.
  hg resolve -m

Whew! Here's hoping this helps someone else!