aegis -clone(1)

NAME
aegis -clone - make an exact copy of a change

SYNOPSIS
aegis -CLone [ option... ] change-number [ change-number ]
aegis -CLone -Help
aegis -CLone -VERSion

DESCRIPTION
The aegis -CLone command is used to create exact replicas of changes. This is of most use when a change need to be applied to several parallel branches.

One change number must be supplied. This is the change to be replicated. If any branch options are given (see below) the mandatory change number applies to the branch specified. If no branch is specified, the change applies to the project (implicit or explicit).

If the optional second change number is supplied, this is the change number to be created to hold the replica; if it is not supplied, the next available change number will be used.

If the change to be replicated has been completed, the appropriate file revisions will be extracted from history; otherwise the files will be copied from the development directory of the change to be copied. Be warned: if a file in the change which was cloned subsequently changes, those changes will not automagically be tracked. It is best if changes are cloned at a stable time, such as one of the states after develop end, or even after integrate pass.

  Development Directory Location
Please Note: Aegis also consults the underlying file system, to determine its notion of maximum file size. Where the file system's maximum file size is less than maximum_filename_length, the filesystem wins. This can happen, for example, when you are using the Linux UMSDOS file system, or when you have an NFS mounted an ancient V7 filesystem. Setting maximum_filename_length to 255 in these cases does not alter the fact that the underlying file systems limits are far smaller (12 and 14, respectively).

If your development directories (or your whole project) is on filesystems with filename limitations, or a portion of the heterogeneous builds take place in such an environment, it helps to tell Aegis what they are (using the project config file's fields) so that you don't run into the situation where the project builds on the more permissive environments, but fails with mysterious errors in the more limited environments.

If your development directories are routinely on a Linux UMSDOS filesystem, you would probably be better off setting dos_filename_required = true, and also changing the development_directory_template field. Heterogeneous development with various Windows environments may also require this.

WHITEOUT
Aegis provides you with what is often called a “view path” which indicates to development tools (compilers, build systems, etc) look first in the development directory, then in the branch baseline, and so on up to the trunk baseline.

The problem with view paths is that in order to remove files, you need some kind of "whiteout" to say “stop looking, it's been removed.”

When you user the aerm(1) or aemv(1) commands, this means "add information to this change which will remove the file from the baseline when this change is integrated". I.e. while the change is in the being developed state, the file is only "removed" in the development directory - it's still present in the baseline, and will be until the change is successfully integrated.

When you use the aerm(1) or aemv(1) commands, Aegis will create a 1K file to act as the whiteout. It's contents are rather ugly so that if you compile or include the "removed" file accidentally, you get a fatal error. This will remind you to remove obsolete references.

When the change in integrated, the removed file is not copied/linked from the baseline to the integration directory, and is not copied from the development directory. At this time it is physically gone (no whiteout). It is assumed that because of the error inducing whiteout all old references were found and fixed while the change was in the being developed state.

  File Manifests
When generating list of files to be compiled or linked, it is important that the file manifest be generated from information known by Aegis, rather than from the file system. This is for several reasons:

(a) Aegis knows exactly what (source) files are where, whereas everything else is inferring Aegis' knowledge; and

(b) looking in the file system is hard when the view path is longer that 2 directories (and Aegis' branching method can make it arbitrarily long); and

(c) The whiteout files, and anything else left “lying around”, will confuse any method which interrogates the file system.

The easiest way to use Aegis' file knowledge is with something like an awk(1) script processing the Aegis file lists. For example, you can do this with make(1) as follows:
    # generate the file manifest
    manifest.make.inc: manifest.make.awk
    	( aegis -l cf -ter ; aegis -l pf -ter ) | \
    	awk -f manifest.make.awk > manifest.make.inc
    # now include the file manifest
    include manifest.make.inc
Note: this would be inefficient of you did it once per directory, but there is nothing stopping you writing numerous assignments into the manifest.make.inc file, all in one pass.

It is possible to do the same thing with Aegis' report generator (see aer(1) for more information), but this is more involved than the awk(1) script. However, with the information "straight from the horse's mouth" as it were, it can also be much smarter.

This file manifest would become out-of-date without an interlock to Aegis' file operations commands. By using the project-file_command and change_file_command fields of the project config file (see aepconf(5) for more information), you can delete this file at strategic times.
    /* run when the change file manifest is altered */
    change_file_command = "rm -f manifest.make.inc";
    /* run when the project file manifest is altered */
    project_file_command = "rm -f manifest.make.inc";
The new file manifest will thus be re-built during the next aeb(1) command.

  Options and Preferences
There is a -No-WhiteOut option, which may be used to suppress whiteout files when you use the aerm(1) and aemv(1) commands. There is a corresponding -WhiteOut option, which is usually the default.

There is a whiteout_preference field in the user preferences file (see aeuconf(5) for more information) if you want to set this option more permanently.

  Whiteout File Templates
The whiteout_template field of the project config file may be used to produce language-specific error files. If no whiteout template entry matches, a very ugly 1KB file will be produced - it should induce compiler errors for just about any language.

If you want a more human-readable error message, entries such as
    whiteout_template =
    [
    	{
    		pattern = [ "*.[ch]" ];
    		body = "#error This file has been removed.";
    	}
    ];
can be very effective (this example assumes gcc(1) is being used).

If it is essential that no whiteout file be produced, say for C source files, you could use a whiteout template such as
    whiteout_template =
    [
    	{ pattern = [ "*.c" ]; }
    ];
because an absent body sub-field means generate no whiteout file at all.

You may have more than one whiteout template entry, but note that the order of the entries is important. The first entry which matches will be used.

  Notification
The notification commands that would be run by the aecp(1), aedb(1), aenf(1), aent(1) and aerm(1) commands are run, as appropriate. The project_file_command is also run, if set. See aepconf(5) for more information.

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.

OPTIONS
The following options are understood:

-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.

-DIRectory path
    This option may be used to specify which directory is to be used. It is an error if the current user does not have appropriate permissions to create the directory path given. This must be an absolute path.

    Caution: If you are using an automounter do not use `pwd` to make an absolute path, it usually gives the wrong answer.

-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.

-WhiteOut
    This option may be used to request that deleted files be replaced by a “whiteout” file in the development directory. The idea is that compiling such a file will result in a fatal error, in order that all references may be found. This is usually the default.

-No_WhiteOut
    This option may be used to request that no “whiteout” file be placed in the development directory.

-Output filename
    This option may be used to specify a filename which is to be written with the automatically determined change number. Useful for writing scripts.

-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.

-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.)

-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.

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.

ERRORS
It is an error if the current user is not an administrator of the project. (In some cases it is possible for developers of a project to create changes, see aepattr(5) for more information.)

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

aenc(1)
    Create a new change.

aeca(1)
    modify the attributes of a change

aena(1)
    add a new administrator to a project

aepa(1)
    modify the attributes of a project

COPYRIGHT
aegis version 4.24.D001
Copyright (C) 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 20 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/