Provided by: aegis_4.24.3-2_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 4.24.3.D001
        Copyright (C) 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999,
        2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010 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/