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.Id $Id: merge.1,v 5.3 1991/02/28 19:18:45 eggert Exp $
.TH MERGE 1 \*(Dt GNU
.SH NAME
merge \- three-way file merge
.SH SYNOPSIS
.B merge
[
.B \-L
.I label1
[
.B \-L
.I label3
] ] [
.B \-p
] [
.B \-q
]
.I "file1 file2 file3"
.SH DESCRIPTION
.B merge
incorporates all changes that lead from
.I file2
to
.I file3
into
.IR file1 .
The result goes to standard output if
.B \-p
is present, into
.I file1
otherwise.
.B merge
is useful for combining separate changes to an original.  Suppose
.I file2
is the original, and both
.I file1
and
.I file3
are modifications of
.IR file2 .
Then
.B merge
combines both changes.
.PP
An overlap occurs if both
.I file1
and
.I file3
have changes in a common segment of lines.
On a few older hosts where
.B diff3
does not support the
.B \-E
option,
.B merge
does not detect overlaps, and merely supplies the changed lines from
.I file3.
On most hosts, if overlaps occur,
.B merge
outputs a message (unless the
.B \-q
option is given),
and includes both alternatives
in the result.  The alternatives are delimited as follows:
.LP
.RS
.nf
.BI <<<<<<< " file1"
.I "lines in file1"
.B "======="
.I "lines in file3"
.BI >>>>>>> " file3"
.RE
.fi
.LP
If there are overlaps, the user should edit the result and delete one of the
alternatives.
If the
.BI \-L "\ label1"
and
.BI \-L "\ label3"
options are given, the labels are output in place of the names
.I file1
and
.I file3
in overlap reports.
.SH DIAGNOSTICS
Exit status is 0 for no overlaps, 1 for some overlaps, 2 for trouble.
.SH IDENTIFICATION
Author: Walter F. Tichy.
.br
Revision Number: \*(Rv; Release Date: \*(Dt.
.br
Copyright \(co 1982, 1988, 1989 by Walter F. Tichy.
.br
Copyright \(co 1990, 1991 by Paul Eggert.
.SH SEE ALSO
diff3(1), diff(1), rcsmerge(1), co(1).