diffutils: diff3 Hunks
7.4 'diff3' Hunks
=================
Groups of lines that differ in two or three of the input files are
called "diff3 hunks", by analogy with 'diff' hunks (⇒Hunks). If
all three input files differ in a 'diff3' hunk, the hunk is called a
"three-way hunk"; if just two input files differ, it is a "two-way
hunk".
As with 'diff', several solutions are possible. When comparing the
files 'A', 'B', and 'C', 'diff3' normally finds 'diff3' hunks by merging
the two-way hunks output by the two commands 'diff A B' and 'diff A C'.
This does not necessarily minimize the size of the output, but
exceptions should be rare.
For example, suppose 'F' contains the three lines 'a', 'b', 'f', 'G'
contains the lines 'g', 'b', 'g', and 'H' contains the lines 'a', 'b',
'h'. 'diff3 F G H' might output the following:
====2
1:1c
3:1c
a
2:1c
g
====
1:3c
f
2:3c
g
3:3c
h
because it found a two-way hunk containing 'a' in the first and third
files and 'g' in the second file, then the single line 'b' common to all
three files, then a three-way hunk containing the last line of each
file.