'\" t
.\"	aegis - project change supervisor
.\"	Copyright (C) 1991, 1992, 1993, 1994, 1995, 1996, 1998, 1999 Peter Miller;
.\"	All rights reserved.
.\"
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.\"	it under the terms of the GNU General Public License as published by
.\"	the Free Software Foundation; either version 2 of the License, or
.\"	(at your option) any later version.
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.\"	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
.\"	GNU General Public License for more details.
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.\"	along with this program; if not, write to the Free Software
.\"	Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111, USA.
.\"
.\" MANIFEST: manual entry for 'aegis -DIFFerence' command
.\"
.so z_name.so
.TH "\*(n) -DIFFerence" 1 \*(N) "Reference Manual"
.SH NAME
\*(n) -DIFFerence \- find differences between a change and the baseline
.XX "aed(1)" "difference a change"
.SH SYNOPSIS
.B \*(n)
.B -DIFFerence
[
.IR filename ...
]
[
.IR option ...
]
.br
.B \*(n)
.B -DIFFerence
.B -List
[
.IR option ...
]
.br
.B \*(n)
.B -DIFFerence
.B -Help
.SH DESCRIPTION
The
.I \*(n)
.I -DIFFerence
command is used to
generate difference listings between source files in the
the development directory and the baseline.
The purpose is to enable reviewers to find each and every edit
performed on the source files.
The difference listings will be placed into files
named for the sources files but
with an additional "\f(CW,D\fP" suffix.
.PP
The command used to perform the differences is specified in the
.I diff_command
field of the project
.I config
file (see
.IR aepconf (5)
for more information).
.PP
If no files are named on the command line,
all files in the change will be differenced.
.PP
You may name a directory on the command line,
and all files in the change in that directory tree will be differenced.
.so z_intuit.so
.so z_bl_lock.so
.SH CONFLICT RESOLUTION
If the version of a file in the change is not the same
as the version of the file in the baseline,
it is out-of-date;
some other change has altered the file while this change was
being developed.
.PP
When a difference is requested for an out-of-date file,
a merge is performed
between the common ancestor,
the version in the baseline,
and the version in the development directory.
The command used to perform the merge is specified by the
.I merge_command
field of the project
.I config
file (see
.IR aepconf (5)
for more information).
.PP
After the merge is performed
the version of the file will be changed to be the current version,
marking the file as up to date,
and a new build will be required.
.PP
The difference output in the \fI,D\fP files
contains the result of the merge.
You should edit them,
to make sure the automatic merge has produced sensible results,
and then rename them to be the corresponding source file.
.PP
This merge process works most of the time.
Usually two changes to two logically separate areas of functionality
will alter two logically separate parts of any files they may
have in common.
There are pathological cases where this merge process is spectacularly
useless,
but these are surprisingly rare in practice.
.PP
If any merges are required no differences will be performed.
An error message and a non-zero exit status will also result.
This is to ensure that developers notice that merges have been done,
and that they reconcile the sources and the merged \fI,D\fP files
before the next difference.
See the
.B -No_Merge
and
.B -Only_Merge
options, below,
for exact control of when merging is performed.
.SH INTEGRATION
During integration, it is also necessary to difference a change.
This provides the difference between the branch and its parent, for
when development on a branch is completed and it is to be reviewed.
The baseline of a branch is the development directory of the composite
change it represents.
.SH OPTIONS
The following options are understood:
.so o_anticip.so
.so o_branch.so
.so o_change.so
.so o_help.so
.so o_list.so
.so o_nolog.so
.so o_trunk.so
.TP 8n
.B -No_Merge
.br
This option is used to
cause only file differences to be generated,
even when file versions are out-of-date.
If not set, the default is to use the
.I diff_preference
field of the
.IR aeuconf (5)
file.
.TP 8n
.B -Only_Merge
.br
This option is used to
cause only file merges to be performed
on files with out-of-date versions.
Other source files are ignored.
If not set, the default is to use the
.I diff_preference
field of the
.IR aeuconf (5)
file.
.TP 8n
.B -Automatic_Merge
.br
This option is used to
perform
.I -Only_Merge
if any source files have out-of-date versions,
otherwise
.I -No_Merge is performed.
Only merges or differences will be performed,
it will never use a mixture.
If not set, the default is to use the
.I diff_preference
field of the
.IR aeuconf (5)
file.
.so o_project.so
.so o_terse.so
.so o_verbose.so
.so o_wait.so
.so o__rules.so
.SH RECOMMENDED ALIAS
The recommended alias for this command is
.nf
.ta 8n 16n
csh%	alias aed '\*(n) -diff \e!* -v'
sh$	aed(){\*(n) -diff "$@" -v}
.fi
For user's convenience,
particularly when they have selected the ``no merge'' preference,
there is also a merge alias:
.nf
.ta 8n 16n
csh%	alias aem '\*(n) -diff -only_merge \e!* -v'
sh$	aem(){\*(n) -diff -only_merge $* -v}
.fi
.SH ERRORS
It is an error if
the change is not in the
.I "being developed"
or
.I "being integrated"
states.
.br
.so z_exit.so
.br
.ne 1i
.SH SEE ALSO
.TP 8n
.IR aeb (1)
build also takes a baseline read lock (non-exclusive)
.TP 8n
.IR aecp (1)
copy file also takes a baseline read lock (non-exclusive)
.TP 8n
.IR aedb (1)
begin development of a change
.TP 8n
.IR aeipass (1)
integrate pass takes a baseline write lock (exclusive)
.TP 8n
.IR aepconf (5)
project configuration file format
.TP 8n
.IR aeuconf (5)
user configuration file format
.so z_cr.so