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(diff.info)diff3 Merging

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Merging From a Common Ancestor
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   When two people have made changes to copies of the same file,
`diff3' can produce a merged output that contains both sets of changes
together with warnings about conflicts.

   One might imagine programs with names like `diff4' and `diff5' to
compare more than three files simultaneously, but in practice the need
rarely arises.  You can use `diff3' to merge three or more sets of
changes to a file by merging two change sets at a time.

   `diff3' can incorporate changes from two modified versions into a
common preceding version.  This lets you merge the sets of changes
represented by the two newer files.  Specify the common ancestor version
as the second argument and the two newer versions as the first and third
arguments, like this:

     diff3 MINE OLDER YOURS

You can remember the order of the arguments by noting that they are in
alphabetical order.

   You can think of this as subtracting OLDER from YOURS and adding the
result to MINE, or as merging into MINE the changes that would turn
OLDER into YOURS.  This merging is well-defined as long as MINE and
OLDER match in the neighborhood of each such change.  This fails to be
true when all three input files differ or when only OLDER differs; we
call this a "conflict".  When all three input files differ, we call the
conflict an "overlap".

   `diff3' gives you several ways to handle overlaps and conflicts.
You can omit overlaps or conflicts, or select only overlaps, or mark
conflicts with special `<<<<<<<' and `>>>>>>>' lines.

   `diff3' can output the merge results as an `ed' script that that can
be applied to the first file to yield the merged output.  However, it
is usually better to have `diff3' generate the merged output directly;
this bypasses some problems with `ed'.

Which Changes

Selecting changes to incorporate.

Marking Conflicts

Marking conflicts.

Bypassing ed

Generating merged output directly.

Merging Incomplete Lines

How `diff3' merges incomplete lines.

Saving the Changed File

Emulating System V behavior.