== Conflict ==

A '''conflict''' occurs when two independent [[ChangeSet|changesets]] modify overlapping sections of a file in different ways.  During a [[Merge|merge]], Mercurial may require the assistance of the user through a 
merge program which can be used to resolve those conflicts.

If the merge program is not a graphical tool,
a common fallback behavior is to use `diff3` for highlighting
the conflict in the file using ''conflict markers''.
A text editor can be used to resolve the conflicts manually.

----

For example:

Given the base file:
{{{
$ cat base
A
B
C
}}}

assuming `local` is your modified copy of `base`:
{{{
$ cat local
A
B - my local changes
C
}}}

and assuming `other` is another modified copy of `base`:
{{{
$ cat other
A
B - changes made by others
C
}}}

then there's obviously a conflicting change on the `B` line.
The "merged" content, as produced by the GNU `diff3` program,
will look like this:
{{{
$ diff3 -m local base other
A
<<<<<<< local
B - my local changes
||||||| base
B
=======
B - changes made by others
>>>>>>> other
C
}}}

See also: TutorialConflict, ImergeExtension
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CategoryGlossary