The
(n) -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
config file (see
aepconf(5) for more information).
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 (n) program will attempt to determine the project file names
from the file names given on the command line.
All file names are stored within (n) 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.
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
"(n) -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 (n)' 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.
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.
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
config file (see
aepconf(5) for more information).
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 difference output in the ,D 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.
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 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.
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:
-ANticipatechange-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.
-BRanchnumber
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.)
-Changenumber
This option may be used to specify a particular change within a project.
When no
-Change option is specified,
the
AEGIS_CHANGE environment variable is consulted.
If that does not exist,
the user's
$HOME/.aegisrc file is examined for a default change field (see
aeuconf(5) for more information).
If that does not exist,
when the user is only working on one change within a project,
that is the default change number.
Otherwise,
it is an error.
-Help
This option may be used to obtain more information about how to use the
(n) 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 (n) 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.
-Projectname
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
$HOME/.aegisrc file is examined for a default project field (see
aeuconf(5) for more information).
If that does not exist,
when the user is only working on changes within a single project,
the project name defaults to that project.
Otherwise,
it is an error.
-TERse
This option may be used to cause listings to
produce the bare minimum of information.
It is usually useful for shell scripts.
-Verbose
This option may be used to cause (n) to produce more output.
By default (n) only produces output on errors.
When used with the
-List option
this option causes column headings to be added.
-Wait
This option may be used to require (N) commands to wait for access
locks, if they cannot be obtained immediately.
Defaults to the user's
lock_wait_preference if not specified, see
aeuconf(5) for more information.
-No_Wait
This option may be used to require (N) commands to emit a fatal error
if access locks cannot be obtained immediately.
Defaults to the user's
lock_wait_preference if not specified, see
aeuconf(5) for more information.
All options may be abbreviated;
the abbreviation is documented as the upper case letters,
all lower case letters and underscores (_) are optional.
You must use consecutive sequences of optional letters.
All options are case insensitive,
you may type them in upper case or lower case or a combination of both,
case is not important.
For example:
the arguments "-project, "-PROJ" and "-p" are
all interpreted to mean the -Project option.
The argument "-prj" will not be understood,
because consecutive optional characters were not supplied.
Options and other command line arguments may be
mixed arbitrarily on the command line,
after the function selectors.
The GNU long option names are understood.
Since all option names for
(n) are long,
this means ignoring the extra leading '-'.
The "--option=value" convention is also understood.
RECOMMENDED ALIAS
The recommended alias for this command is
csh% alias aed '(n) -diff \!* -v'
sh$ aed(){(n) -diff "$@" -v}
For user's convenience,
particularly when they have selected the ``no merge'' preference,
there is also a merge alias:
Copyright (C) (Y) Peter Miller;
All rights reserved.
The (n) program comes with ABSOLUTELY NO WARRANTY;
for details use the '(n) -VERSion License' command.
This is free software
and you are welcome to redistribute it under certain conditions;
for details use the '(n) -VERSion License' command.
