+This directory contains complete sources for RCS version 5.6.
+
+RCS, the Revision Control System, manages multiple revisions of files.
+RCS can store, retrieve, log, identify, and merge revisions.
+It is useful for files that are revised frequently,
+e.g. programs, documentation, graphics, and papers.
+
+/* Copyright (C) 1982, 1988, 1989 Walter Tichy
+ Copyright 1990, 1991 by Paul Eggert
+ Distributed under license by the Free Software Foundation, Inc.
+
+This file is part of RCS.
+
+RCS is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 2, or (at your option)
+any later version.
+
+RCS is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with RCS; see the file COPYING. If not, write to
+the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
+
+Report problems and direct all questions to:
+
+ rcs-bugs@cs.purdue.edu
+
+*/
+
+$Id: README,v 5.16 1991/11/03 01:09:19 eggert Exp $
+
+
+Installation notes:
+
+ RCS requires a diff that supports the -n option.
+ Get GNU diff (version 1.15 or later) if your diff lacks -n.
+
+ RCS works best with a diff that supports -a and -L,
+ and a diff3 that supports -E and -m.
+ GNU diff supports these options.
+
+ Sources for RCS are in the src directory.
+ Read the directions in src/README to build RCS on your system.
+
+ Manual entries reside in man.
+
+ Troff source for the paper `RCS--A System for Version Control', which
+ appeared in _Software--Practice & Experience_, is in rcs.ms.
+
+ If you don't have troff, you can get GNU groff to format the documentation.
+
+
+RCS compatibility notes:
+
+ RCS version 5 reads RCS files written by any RCS version released since 1982.
+ It also writes RCS files that these older versions of RCS can read,
+ unless you use one of the following new features:
+
+ checkin times after 1999/12/31 23:59:59 GMT
+ checking in non-text files
+ non-Ascii symbolic names
+ rcs -bX, where X is nonempty
+ rcs -kX, where X is not `kv'
+ RCS files that exceed hardcoded limits in older RCS versions
+
+ A working file written by RCS 5.5 or later contains four-digit years in its
+ keyword strings. If you check out a working file with RCS 5.5 or later,
+ an older RCS version's `ci -k' may insist on two-digit years.
+ Fix this with `co -V4', or by editing the working file.
+
+
+Features new to RCS version 5.6 include:
+
+ Security holes have been plugged; setgid use is no longer supported.
+
+ co can retrieve old revisions much more efficiently.
+ To generate the Nth youngest revision on the trunk,
+ the old method used up to N passes through copies of the working file;
+ the new method uses a piece table to generate the working file in one pass.
+
+ When ci finds no changes in the working file,
+ it automatically reverts to the previous revision unless -f is given.
+
+ RCS follows symbolic links to RCS files instead of breaking them,
+ and warns when it breaks hard links to RCS files.
+
+ `$' stands for the revision number taken from working file keyword strings.
+ E.g. if F contains an Id keyword string,
+ `rcsdiff -r$ F' compares F to its checked-in revision, and
+ `rcs -nL:$ F' gives the symbolic name L to F's revision.
+
+ co and ci's new -M option sets the modification time
+ of the working file to be that of the revision.
+ Without -M, ci now tries to avoid changing the working file's
+ modification time if its contents are unchanged.
+
+ rcs's new -m option changes the log message of an old revision.
+
+ RCS is portable to hosts that do not permit `,' in filenames.
+ (`,' is not part of the Posix portable filename character set.)
+ A new -x option specifies extensions other than `,v' for RCS files.
+ The Unix default is `-x,v/', so that the working file `w' corresponds
+ to the first file in the list `RCS/w,v', `w,v', `RCS/w' that works.
+ The non-Unix default is `-x', so that only `RCS/w' is tried.
+ Eventually, the Unix default should change to `-x/,v'
+ to encourage interoperability among all Posix hosts.
+
+ A new RCSINIT environment variable specifies defaults for options like -x.
+
+ The separator for revision ranges has been changed from `-' to `:', because
+ the range `A-B' is ambiguous if `A', `B' and `A-B' are all symbolic names.
+ E.g. the old `rlog -r1.5-1.7' is now `rlog -r1.5:1.7'; ditto for `rcs -o'.
+ For a while RCS will still support (but warn about) the old `-' separator.
+
+ RCS manipulates its lock files using a method that is more reliable under NFS.
+
+ Experimental support for MS-DOS and OS/2 is available as part of a separate
+ software distribution.
+
+
+Features new to RCS version 5 include:
+
+ RCS can check in arbitrary files, not just text files, if diff -a works.
+ RCS can merge lines containing just a single `.' if diff3 -m works.
+ GNU diff supports the -a and -m options.
+
+ RCS can now be used as a setuid program.
+ See ci(1) for how users can employ setuid copies of ci, co, and rcsclean.
+ Setuid privileges yield extra security if the effective user owns RCS files
+ and directories, and if only the effective user can write RCS directories.
+ RCS uses the real user for all accesses other than writing RCS directories.
+ As described in ci(1), there are three levels of setuid support.
+
+ 1. Setuid works fully if the seteuid() system call lets any
+ process switch back and forth between real and effective users,
+ as specified in Posix 1003.1a Draft 5.
+
+ 2. On hosts with saved setuids (a Posix 1003.1-1990 option) and without
+ a modern seteuid(), setuid works unless the real or effective user is root.
+
+ 3. On hosts that lack both modern seteuid() and saved setuids,
+ setuid does not work, and RCS uses the effective user for all accesses;
+ formerly it was inconsistent.
+
+ New options to co, rcsdiff, and rcsmerge give more flexibility to keyword
+ substitution.
+
+ -kkv substitutes the default `$Keyword: value $' for keyword strings.
+ However, a locker's name is inserted only as a file is being locked,
+ i.e. by `ci -l' and `co -l'. This is normally the default.
+
+ -kkvl acts like -kkv, except that a locker's name is always inserted
+ if the given revision is currently locked. This was the default in
+ version 4. It is now the default only with when using rcsdiff to
+ compare a revision to a working file whose mode is that of a file
+ checked out for changes.
+
+ -kk substitutes just `$Keyword$', which helps to ignore keyword values
+ when comparing revisions.
+
+ -ko retrieves the old revision's keyword string, thus bypassing keyword
+ substitution.
+
+ -kv retrieves just `value'. This can ease the use of keyword values, but
+ it is dangerous because it causes RCS to lose track of where the keywords
+ are, so for safety the owner write permission of the working file is
+ turned off when -kv is used; to edit the file later, check it out again
+ without -kv.
+
+ rcs -ko sets the default keyword substitution to be in the style of co -ko,
+ and similarly for the other -k options. This can be useful with binary file
+ formats that cannot tolerate changing the lengths of keyword strings.
+ However it also renders a RCS file readable only by RCS version 5 or later.
+ Use rcs -kkv to restore the usual default substitution.
+
+ RCS can now be used by development groups that span timezone boundaries.
+ All times are now displayed in GMT, and GMT is the default timezone.
+ To use local time with co -d, append ` LT' to the time.
+ When interchanging RCS files with sites running older versions of RCS,
+ time stamp discrepancies may prevent checkins; to work around this,
+ use `ci -d' with a time slightly in the future.
+
+ Dates are now displayed using four-digit years, not two-digit years.
+ Years given in -d options must now have four digits.
+ This change is required for RCS to continue to work after 1999/12/31.
+ The form of dates in version 5 RCS files will not change until 2000/01/01,
+ so in the meantime RCS files can still be interchanged with sites
+ running older versions of RCS. To make room for the longer dates,
+ rlog now outputs `lines: +A -D' instead of `lines added/del: A/D'.
+
+ To help prevent diff programs that are broken or have run out of memory
+ from trashing an RCS file, ci now checks diff output more carefully.
+
+ ci -k now handles the Log keyword, so that checking in a file
+ with -k does not normally alter the file's contents.
+
+ RCS no longer outputs white space at the ends of lines
+ unless the original working file had it.
+ For consistency with other keywords,
+ a space, not a tab, is now output after `$Log:'.
+ Rlog now puts lockers and symbolic names on separate lines in the output
+ to avoid generating lines that are too long.
+ A similar fix has been made to lists in the RCS files themselves.
+
+ RCS no longer outputs the string `Locker: ' when expanding Header or Id
+ keywords. This saves space and reverts back to version 3 behavior.
+
+ The default branch is not put into the RCS file unless it is nonempty.
+ Therefore, files generated by RCS version 5 can be read by RCS version 3
+ unless they use the default branch feature introduced in version 4.
+ This fixes a compatibility problem introduced by version 4.
+
+ RCS can now emulate older versions of RCS; see `co -V'.
+ This may be useful to overcome compatibility problems
+ due to the above changes.
+
+ Programs like Emacs can now interact with RCS commands via a pipe:
+ the new -I option causes ci, co, and rcs to run interactively,
+ even if standard input is not a terminal.
+ These commands now accept multiple inputs from stdin separated by `.' lines.
+
+ ci now silently ignores the -t option if the RCS file already exists.
+ This simplifies some shell scripts and improves security in setuid sites.
+
+ Descriptive text may be given directly in an argument of the form -t-string.
+
+ The character set for symbolic names has been upgraded
+ from Ascii to ISO 8859.
+
+ rcsdiff now passes through all options used by GNU diff;
+ this is a longer list than 4.3BSD diff.
+
+ merge's new -L option gives tags for merge's overlap report lines.
+ This ability used to be present in a different, undocumented form;
+ the new form is chosen for compatibility with GNU diff3's -L option.
+
+ rcsmerge and merge now have a -q option, just like their siblings do.
+
+ RCS now attempts to ignore parts of an RCS file that look like they come
+ from a future version of RCS.
+
+ When properly configured, RCS now strictly conforms with Posix 1003.1-1990.
+ RCS can still be compiled in non-Posix traditional Unix environments,
+ and can use common BSD and USG extensions to Posix.
+ RCS is a conforming Standard C program, and also compiles under traditional C.
+
+ Arbitrary limits on internal table sizes have been removed.
+ The only limit now is the amount of memory available via malloc().
+
+ File temporaries, lock files, signals, and system call return codes
+ are now handled more cleanly, portably, and quickly.
+ Some race conditions have been removed.
+
+ A new compile-time option RCSPREFIX lets administrators avoid absolute path
+ names for subsidiary programs, trading speed for flexibility.
+
+ The configuration procedure is now more automatic.
+
+ Snooping has been removed.
+
+
+Version 4 was the first version distributed by FSF.
+Beside bug fixes, features new to RCS version 4 include:
+
+ The notion of default branch has been added; see rcs -b.
+
+
+Version 3 was included in the 4.3BSD distribution.
+
+
+Further projects:
+
+ Add format options for finer control over the output of ident and rlog.
+
+ Be able to redo the most recent checkin with minor changes.
+
+ Add a `-' option to take the list of pathnames from standard input.
+ Perhaps the pathnames should be null-terminated, not newline-terminated,
+ so that pathnames that contain newlines are handled properly.
+
+ Add general options so that rcsdiff and rcsmerge can pass arbitrary options
+ to its subsidiary co and diff processes. E.g.
+
+ -.OPTION to pass OPTION to the subsidiary `co'
+ -/OPTION to pass OPTION to the subsidiary `diff' (for rcsdiff only)
+
+ For example:
+
+ rcsdiff -.-d"1991/02/09 18:09" -.-sRel -/+unified -/-C -/5 -/-d foo.c
+
+ invokes `co -d"1991/02/09 18:09" -sRel ...' and `diff +unified -C 5 -d ...'.
+ To pass an option to just one subsidiary `co', put the -. option
+ after the corresponding -r option. For example:
+
+ rcsmerge -r1.4 -.-ko -r1.8 -.-kkv foo.c
+
+ passes `-ko' to the first subsidiary `co', and `-kkv' to the second one.
+
+
+ Permit multiple option-pathname pairs, e.g. co -r1.4 a -r1.5 b.
+
+ Add ways to specify the earliest revision, the most recent revision,
+ the earliest or latest revision on a particular branch, and
+ the parent or child of some other revision.
+
+ If a user has multiple locks, perhaps ci should fall back on ci -k's
+ method to figure out which revision to use.
+
+ Symbolic names need not refer to existing branches and revisions.
+ rcs(1)'s BUGS section says this is a bug. Is it? If so, it should be fixed.
+
+ Write an rcsck program that repairs corrupted RCS files,
+ much as fsck repairs corrupted file systems.
+
+ Clean up the source code with a consistent indenting style.
+
+ Update the date parser to use the more modern getdate.y by Bellovin,
+ Salz, and Berets, or the even more modern getdate by Moraes. None of
+ these getdate implementations are as robust as RCS's old warhorse in
+ avoiding problems like arithmetic overflow, so they'll have to be
+ fixed first.
+
+ Break up the code into a library so that it's easier to write new programs
+ that manipulate RCS files, and so that useless code is removed from the
+ existing programs. For example, the rcs command contains unnecessary
+ keyword substitution baggage, and the merge command can be greatly pruned.
+
+ Make it easier to use your favorite text editor to edit log messages,
+ etc. instead of having to type them in irretrievably at the terminal.
+
+The following projects require a change to RCS file format,
+and thus must wait until at least RCS version 6.
+
+ Be able to store RCS files in compressed format.
+ Don't bother to use a .Z extension that would exceed file name length limits;
+ just look at the magic number.
+
+ Add locker commentary, e.g. `co -l -m"checkout to fix merge bug" foo'
+ to tell others why you checked out `foo'.
+ Also record the time when the revision was locked,
+ and perhaps the working pathname (if applicable).
+
+ Let the user mark an RCS revision as deleted; checking out such a revision
+ would result in no working file. Similarly, using `co -d' with a date either
+ before the initial revision or after the file was marked deleted should
+ remove the working file. For extra credit, extend the notion of `deleted' to
+ include `renamed'. RCS should support arbitrary combinations of renaming and
+ deletion, e.g. renaming A to B and B to A, checking in new revisions to both
+ files, and then renaming them back.
+
+ Use a better scheme for locking revisions; the current scheme requires
+ changing the RCS file just to lock or unlock a revision.
+ The new scheme should coexist as well as possible with older versions of RCS,
+ and should avoid the rare NFS bugs mentioned in rcsedit.c.
+
+ Add rcs options for changing keyword names, e.g. XConsortium instead of Id.
+
+ Add frozen branches a la SCCS. In general, be able to emulate all of
+ SCCS, so that an SCCS-to-RCS program can be practical.
+
+ Add support for distributed RCS, where widely separated
+ users cannot easily access each others' RCS files,
+ and must periodically distribute and reconcile new revisions.
+
+ Be able to create empty branches.
+
+ Improve RCS's method for storing binary files.
+ Although it is more efficient than SCCS's,
+ the diff algorithm is still line oriented,
+ and often generates long output for minor changes to an executable file.
+
+ Add a new `-kb' expansion for binary files on non-Posix hosts
+ that distinguish between text and binary I/O.
+ The current `text_work_stdio' compile-time switch is too inflexible.
+ This fix either requires nonstandard primitives like DOS's setmode(),
+ or requires that `-kb' be specified on initial checkin and never changed.
+ From the user's point of view, it would be best if
+ RCS detected and handled binary files without human intervention,
+ switching expansion methods as needed from revision to revision.
+
+ Extend the grammar of RCS files so that keywords need not be in a fixed order.
+
+ Internationalize messages; unfortunately, there's no common standard yet.
+ This requires a change in RCS file format because of the
+ `empty log message' and `checked in with -k' hacks inside RCS files.
+
+
+Credits:
+
+ RCS was designed and built by Walter F. Tichy of Purdue University.
+ RCS version 3 was released in 1983.
+
+ Adam Hammer, Thomas Narten, and Dan Trinkle of Purdue supported RCS through
+ version 4.3, released in 1990. Guy Harris of Sun contributed many porting
+ fixes. Paul Eggert of System Development Corporation contributed bug fixes
+ and tuneups. Jay Lepreau contributed 4.3BSD support.
+
+ Paul Eggert of Twin Sun wrote the changes for RCS version 5, released in 1991.
+ Rich Braun of Kronos and Andy Glew of Intel contributed ideas for new options.
+ Bill Hahn of Stratus contributed ideas for setuid support.
+ Ideas for piece tables came from Joe Berkovitz of Stratus and Walter F. Tichy.
+ Matt Cross of Stratus contributed test case ideas.
+ Adam Hammer of Purdue QAed.
projects / unix-history / commitdiff