Provided by: aegis_4.24.2-4_i386 bug

NAME

       aegis -DIFFerence - find differences between a change and the baseline

SYNOPSIS

       aegis -DIFFerence [ filename...  ] [ option...  ]
       aegis -DIFFerence -List [ option...  ]
       aegis -DIFFerence -Help

DESCRIPTION

       The aegis -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 ",D"
       suffix.

       The command used to perform the differences is specified in the
       diff_command field of the project configuration file (see aepconf(5)
       for more information).

       It is possible to configure a project to omit the diff step as
       unnecessary, by the following setting:
              diff_command = "exit 0";
       This disables all generation, checking and validation of difference
       file for each change source file.  The merge functions of the aediff(1)
       command are unaffected by this setting.

       Please note that the history_content_limitation field of the project
       configuration file does not apply to the diff_command field.

       If no files are named on the command line, all files in the change will
       be differenced.

       You may name a directory on the command line, and all files in the
       change in that directory tree will be differenced.

   File Name Interpretation
       The aegis program will attempt to determine the project file names from
       the file names given on the command line.  All file names are stored
       within aegis projects as relative to the root of the baseline directory
       tree.  The development directory and the integration directory are
       shadows of this baseline directory, and so these relative names apply
       here, too.  Files named on the command line are first converted to
       absolute paths if necessary.  They are then compared with the baseline
       path, the development directory path, and the integration directory
       path, to determine a baseline-relative name.  It is an error if the
       file named is outside one of these directory trees.

       The -BAse_RElative option may be used to cause relative filenames to be
       interpreted as relative to the baseline path; absolute filenames will
       still be compared with the various paths in order to determine a
       baseline-relative name.

       The relative_filename_preference in the user configuration file may be
       used to modify this default behavior.  See aeuconf(5) for more
       information.

   Notification
       The actions of the command are controlled by the diff_command and
       merge_command fields of the project config file.  See aepconf(5) for
       more information.

THE BASELINE LOCK

       The baseline lock is used to ensure that the baseline remains in a
       consistent state for the duration of commands which need to read the
       contents of files in the baseline.

       The commands which require the baseline to be consistent (these include
       the aeb(1), aecp(1) and aed(1) commands) take a baseline read lock.
       This is a non-exclusive lock, so the concurrent development of changes
       is not hindered.

       The command which modifies the baseline, aeipass(1), takes a baseline
       write lock.  This is an exclusive lock, forcing aeipass(1) to block
       until there are no active baseline read locks.

       It is possible that one of the above development commands will block
       until an in-progress aegis -Integrate_PASS completes.  This is usually
       of short duration while the project history is updated.  The delay is
       essential so that these commands receive a consistent view of the
       baseline.  No other integration command will cause the above
       development commands to block.

       When aegis’ branch functionality is in use, a read (non-exclusive) lock
       is taken on the branch baseline and also each of the "parent"
       baselines.  However, a baseline write (exclusive) lock is only taken on
       the branch baseline; the "parent" baselines are only read (non-
       exclusive) locked.

   File Action Adjustment
       When this command runs, it first checks the change files against the
       projects files.  If there are inconsistencies, the file actions will be
       adjusted as follows:

       create  If a file is being created, but another change set is
               integrated which also creates the file, the file action in the
               change set still being developed will be adjusted to "modify".

       modify  If a file is being modified, but another change set is
               integrated which removes the file, the file action in the
               change set still being developed will be adjusted to "create".

       remove  If a file is being removed, but another change set is
               integrated which removes the file, the file will be dropped
               from the change set still being developed.

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.

       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 merge_command field of the project
       configuration file (see aepconf(5) for more information).

       Please note that the history_content_limitation field of the project
       configuration file does not apply to the merge_command field.

       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.

       The original file in your development directory is preserved with an
       ",B" suffix (B for backup).  The source file contains the result of the
       merge.  You should edit the source files, to make sure the automatic
       merge has produced sensible results.

       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.

       If you don’t want the automatic merge results, simply use the mv(1)
       command to restore the contents from the ",B" file.

       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 ,D files before the next
       difference.  See the -No_Merge and -Only_Merge options, below, for
       exact control of when merging is performed.

Cloning and Merging

       When you use aeclone(1) to clone a change set, and then integrate one
       of the two change sets, you will observe that Aegis says that the files
       of the un-integrated change are now out-of-date.

       If you run aem(1) to bring the out-of-date files back up-to-date,
       fmerge(1) and some (but not) all other merging tools, it signals just
       about everything as a conflict, even though both alternatives are
       identical.

       The problem is that two changes making identical edits to the same
       place in the same file are a logical conflict, even if not an actual
       conflict, and it takes a human to figure out the difference.  Think of
       a shopping list: the ensuite needs more soap, and so does the main
       bathroom.  The second "soap" on the merge of the two shopping lists
       isn’t a duplicate, you really do need two boxes of soap.  Sometimes
       edits of source files are the same: sometimes the logical conflict is
       resolved by applying both identical edits, not just one.

       This is just the fmerge(1) command being more conservative than RCS’s
       merge(1) command.

       The easiest way to deal with this common situation it to run an
              aecpu -unchanged
       command before you run the aem(1) merge command, and you will have less
       grief.  It’s also worth remembering that Aegis stashes the original
       file with a ,B suffix (B for backup) so you can simply
              mv fubar,B fubar
       if you know that all of the conflicts are logical conflicts.

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.

OPTIONS

       The following options are understood:

       -ANticipate change-number
               This option is used to nominate a source for the reference
               files, rather than the baseline.  This may be used to
               synchronize with a change without having to wait for it to
               arrive in the baseline.  It is an error if the anticipated
               change is not in one of the being reviewed or awaiting
               integration or being integrated states.  A merge is always
               performed, because the anticipated change is "about" to make
               any common file out-of-date.  You will still have to perform a
               "real" merge later.

       -BRanch number
               This option may be used to specify a different branch for the
               origin file, rather than the baseline.  (See also -TRunk
               option.  Please Note: the -BRanch option does not take a
               project name, just the branch number suffix.

       -GrandParent
               This option may be used to specify the grandparent branch (one
               up from the current branch) for the origin file, rather than
               the baseline.  (The -grandparent option is the same as the
               “-branch ..” option.)

       -Change number
               This option may be used to specify a particular change within a
               project.  See aegis(1) for a complete description of this
               option.

       -Help
               This option may be used to obtain more information about how to
               use the aegis program.

       -List
               This option may be used to obtain a list of suitable subjects
               for this command.  The list may be more general than expected.

       -Not_Logging
               This option may be used to disable the automatic logging of
               output and errors to a file.  This is often useful when several
               aegis commands are combined in a shell script.

       -TRunk
               This option may be used to specify the project trunk for the
               origin file, rather than the baseline.  (See also -BRanch
               option, the -trunk option is the same as the “-branch -”
               option.)

       -No_Merge
               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 diff_preference field of the
               aeuconf(5) file.

       -Only_Merge
               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 diff_preference
               field of the aeuconf(5) file.

       -Automatic_Merge
               This option is used to perform -Only_Merge if any source files
               have out-of-date versions, otherwise -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
               diff_preference field of the aeuconf(5) file.

       -Project name
               This option may be used to select the project of interest.
               When no -Project option is specified, the AEGIS_PROJECT
               environment variable is consulted.  If that does not exist, the
               user’s $HOME/.aegisrc file is examined for a default project
               field (see aeuconf(5) for more information).  If that does not
               exist, when the user is only working on changes within a single
               project, the project name defaults to that project.  Otherwise,
               it is an error.

       -TERse
               This option may be used to cause listings to produce the bare
               minimum of information.  It is usually useful for shell
               scripts.

       -Verbose
               This option may be used to cause aegis to produce more output.
               By default aegis only produces output on errors.  When used
               with the -List option this option causes column headings to be
               added.

       -Wait   This option may be used to require Aegis commands to wait for
               access locks, if they cannot be obtained immediately.  Defaults
               to the user’s lock_wait_preference if not specified, see
               aeuconf(5) for more information.

       -No_Wait
               This option may be used to require Aegis commands to emit a
               fatal error if access locks cannot be obtained immediately.
               Defaults to the user’s lock_wait_preference if not specified,
               see aeuconf(5) for more information.

       See also aegis(1) for options common to all aegis commands.

       All options may be abbreviated; the abbreviation is documented as the
       upper case letters, all lower case letters and underscores (_) are
       optional.  You must use consecutive sequences of optional letters.

       All options are case insensitive, you may type them in upper case or
       lower case or a combination of both, case is not important.

       For example: the arguments "-project, "-PROJ" and "-p" are all
       interpreted to mean the -Project option.  The argument "-prj" will not
       be understood, because consecutive optional characters were not
       supplied.

       Options and other command line arguments may be mixed arbitrarily on
       the command line, after the function selectors.

       The GNU long option names are understood.  Since all option names for
       aegis are long, this means ignoring the extra leading ’-’.  The
       "--option=value" convention is also understood.

RECOMMENDED ALIAS

       The recommended alias for this command is
       csh%    alias aed ’aegis -diff \!* -v’
       sh$     aed(){aegis -diff "$@" -v}
       For user’s convenience, particularly when they have selected the “no
       merge” preference, there is also a merge alias:
       csh%    alias aem ’aegis -diff -only_merge \!* -v’
       sh$     aem(){aegis -diff -only_merge $* -v}

ERRORS

       It is an error if the change is not in the being developed or being
       integrated states.

EXIT STATUS

       The aegis command will exit with a status of 1 on any error.  The aegis
       command will only exit with a status of 0 if there are no errors.

ENVIRONMENT VARIABLES

       See aegis(1) for a list of environment variables which may affect this
       command.  See aepconf(5) for the project configuration file’s project_
       specific field for how to set environment variables for all commands
       executed by Aegis.

SEE ALSO

       aeb(1)  build also takes a baseline read lock (non-exclusive)

       aecp(1) copy file also takes a baseline read lock (non-exclusive)

       aedb(1) begin development of a change

       aeipass(1)
               integrate pass takes a baseline write lock (exclusive)

       aepconf(5)
               project configuration file format

       aeuconf(5)
               user configuration file format

COPYRIGHT

       aegis version 4.24.2.D001
       Copyright (C) 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999,
       2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009 Peter Miller

       The aegis program comes with ABSOLUTELY NO WARRANTY; for details use
       the ’aegis -VERSion License’ command.  This is free software and you
       are welcome to redistribute it under certain conditions; for details
       use the ’aegis -VERSion License’ command.

AUTHOR

       Peter Miller   E-Mail:   millerp@canb.auug.org.au
       /\/\*             WWW:   http://www.canb.auug.org.au/~millerp/