.ig
 Copyright (C) 1993,1994 by the author(s).
 
 This software is published in the hope that it will be useful, but
 WITHOUT ANY WARRANTY for any part of this software to work correctly
 or as described in the manuals. See the ShapeTools Public License
 for details.

 Permission is granted to use, copy, modify, or distribute any part of
 this software but only under the conditions described in the ShapeTools 
 Public License. A copy of this license is supposed to have been given
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 things, this copyright notice and the Public License must be
 preserved on all copies.


Author: Axel Mahler (Axel.Mahler@cs.tu-berlin.de)

$Header: vdiff.1[4.0] Tue Jun 29 16:42:06 1993 andy@cs.tu-berlin.de frozen $
..
.TH vdiff 1 "Tue Jun 29 16:42:06 1993" "vc_scripts-2.5" "ShapeTools"
.SH NAME
vdiff \- display line-by-line differences between versions of files
.SH SYNOPSIS
\fBvdiff\fR\ [\ \fIdiff-options\fR\ ]\ [\ \fB\-base\ \fIpath\fR\ ]\ [\ \fB\-P\fR\ ]\ files\ \.\|.
.SH DESCRIPTION
.PP
\fBvdiff\fP is a differential comparator for file versions that are
stored in \fIshapeTools'\fP object base, \fIAtFS\fR. The functionality
of \fBvdiff\fP is very similar to the \fBdiff\fP command on your
host. All options and switches that are recognized by \fBdiff\fP can
also be specified for \fBvdiff\fP.
.PP
The arguments to \fBvdiff\fP can either be a single filename, or a
pair of \fIversion identifiers\fP. If only a filename is specified,
\fBvdiff\fP prints the differences between the specified file and the
most recent version of this file that is stored in the AtFS object
base. A file can be compared to any stored version by specifying
the version as first, and the filename as second argument. If both
arguments are version identifiers, the difference between these two
versions is printed. 
.PP
Differences between files and versions can be printed in any style
that is supported by the local \fBdiff\fP program.
.PP
Version identifiers consist of the filename, and a version number or
alias name for a version, enclosed in brackets. Example:
.ce
\fCretrieve.c[4.22]\fP    or    \fCretrieve.c[Rel-4.1]\fP
.PP
\fBvdiff\fP creates temporary copies of the versions that shall be
compared, invokes the \fBdiff\fP command, and finally removes the temporary
copies. 
.SH OPTIONS
.IP "\fB\-base\fP\ \fIpath\fP"
If \fBvdiff\fP is told to produce a \fIcontext diff\fP, the filenames
of the compared objects are mangeled so that the specified \fIpath\fP
replaces the path of the current directory in the full pathnames
appearing in the diff-header. This is useful to replace an absolute
pathname by a relative pathname and makes the produced context-diff
easier to digest for the \fBpatch\fP program.
.IP \fB\-P\fP
With the \fB\-P\fP switch turned on, \fBvdiff\fP won't give up if one
of the two objects that shall be compared does not exist. In this case an
empty object is substituted for the missing one, causing the diff to
be the complete contents of the existing object. This is useful in
situations when complex patches are produced that upgrade one release
of a software system to a new release, and the system has structurally
changed (i.e. new files have been added to the system).
.SH SEE ALSO
diff(1), vcat(1)
.SH AUTHOR
Axel.Mahler@cs.tu-berlin.de