NEWS for GNU RCS (Revision Control System)
See the end for copying conditions.


- 5.9.0 | 2013-05-06

  - distribution now .tar.lz and .tar.xz

	If you have GNU tar, you can use "tar xf" and it will DTRT.
	If not, you can use "lzip -dc TARBALL | tar xf -" to unpack
	the .tar.lz, or "xz -dc TARBALL | tar xf -" for the .tar.xz.

  - planned retirement

    - configure option ‘--enable-compat2’

	This option enables reading of files written by RCS 2.x (before
	RCS was GNU, even), but the file format became obsolete in 1982.
	Support for it WILL BE REMOVED in a near future GNU RCS release.

    - common option ‘-V’

	This option is obsoleted by ‘--version’ (since 5.8, 2011-08-30).
	Support for it WILL BE REMOVED in some future GNU RCS release.
	Its use now produces a warning to stderr.

	Please note that ‘-VN’ (N ∈ {3,4,5}) is a separate issue.

  - bugs fixed

    - ‘rcsmerge --help’ mentions ‘-A’, ‘-E’, ‘-e’

	These options are accepted and internally passed to diff3(1).

    - ‘ident -VN’ and ‘merge -VN’ now signal error

	For these commands, the argument to ‘-V’ has no meaning.
	Previously, such invocations would display version info,
	ignoring the arg.  Now they signal a "bad option" error.

  - new features

    - ident(1) recognizes Subversion "fixed-width keyword syntax"

	In addition to the normal keyword pattern, for Subversion 1.2
	(and later) compatability, ident(1) also recognizes patterns
	having one of the forms:

	$KEYWORD:: TEXT $
	;; two colons and space after keyword
	;; space before ending $

	$KEYWORD:: TEXT#$
	;; two colons and space after keyword
	;; hash before ending $

    - new co(1) option ‘-S’ for "self-same" mode

	In this mode, the owner of a lock is unimportant, just that it
	exists.  Effectively, this prevents you from checking out the
	same revision twice.

	$ whoami
	  ttn

	$ co -l -f z
	  RCS/z,v  -->  z
	  revision 1.1 (locked)
	  done

	$ co -S -l -f z
	  RCS/z,v  -->  z
	  co: RCS/z,v: Revision 1.1 is already locked by ttn.

    - several RCS commands "internalized" into rcs(1)

	As part of an ongoing effort to modernize the command-line
	interface of GNU RCS, the previously standalone programs:

	  ci, co, rcs, rcsclean, rcsdiff, rcsmerge, rlog

	can now be invoked as "rcs PROGRAM".  In this case, we call
	PROGRAM a "command", and also provide some aliases.  E.g., you
	can type "rcs diff" in addition to "rcs rcsdiff" (and "rcsdiff",
	of course).  We plan to support standalone (w/o "rcs" prefix)
	invocation from the shell at least through the 5.x series of
	releases -- not indefinitely, but for a good while, yet.

	The rcs(1) program itself now supports ‘--commands’ to list all
	the commands, ‘--aliases’ to list their aliases, as well as
	‘--help COMAMND’ to show the help for COMMAND.

	Note that programs ident(1) and merge(1) remain standalone.

	Lastly, in the manual, section "Invoking rcs" now describes both
	"modern" and "legacy" usages.  Also, the internalized commands
	invocations mentions both "rcs COMMAND" and "PROGRAM" styles.

    - ‘--help’ output includes a one-line description

	E.g., "merge --help" says: "Three-way file merge".

    - most long options can be recognized if partially specified

	With the exception of "rcs --help COMMAND", where "--help" must
	be spelled out in full, all long options can now be recognized
	even if partially specified.  For example, "rcs --al" is
	recognized as "rcs --aliases".

    - updated portability

	Several more Gnulib (http://www.gnu.org/software/gnulib) modules
	are now in use.

    - new cross-compilation support

	The configure script now assigns "pessimistic defaults" when
	cross-compiling.  See new section "cross-compilation" in README.

    - effects of ‘-VN’ (N ∈ {3,4,5}) documented

	See (info "(rcs) Misc common options").

  - maintenance tools updated
    - gnulib-tool (GNU gnulib 2013-05-01 06:14:19) 0.0.7913-5191


- 5.8.2 | 2013-04-04

  - Bugs fixed

    - Wrong symbolic name dereference

	RCS 5.8 introduced a bug whereby commands would incorrectly
	dereference a symbolic name (into a numerical revision number)
	in the presence of multiple symbolic names that share a common
	prefix.  See tests/t803.

    - ‘integrity’ value syntax better specified

	The ‘integrity’ value (if present) is a string composed of a
	system part followed by an optional user part, with formfeed
	(^L, U+0C) separating the two.  Unlike other string values, the
	‘integrity’ string (either part) must NOT contain '@' (U+40).
	If it does, RCS displays a "spurious '@' in `integrity' value"
	error message and exits failurefully.

	This change restores interop play-space for third-party tools
	that was stricken w/ the RCS 5.8 top-level grammar freeze.  Left
	unspecified is how such tools should divvy up the user part.

  - New manual chapter: RCS file format

	This documents the RCS file format grammar and particulars,
	adapted from rcsfile(5).

  - Manpages refer to info documentation

	They now recommend using "info rcs" for full documentation.

  - Script to trim "junk at end of file" posted

	The "junk at end of file" error occurs for some files due to RCS
	5.8 being more strict about the syntax it accepts.  You can use
	‘trimrcs’ by Warren Jones:

	http://lists.gnu.org/archive/html/help-rcs/2013-01/msg00006.html

	to remedy such files while we figure out how best to move such
	functionality into RCS proper.

  - Maintenance tools updated
    - automake (GNU Automake) 1.13.1
    - gnulib-tool (GNU gnulib 2013-03-19 16:08:47) 0.0.7899-34f84
    - makeinfo (GNU Texinfo) 5.1


- 5.8.1 | 2012-06-05

  - Bugs fixed

    - Debug output removed

	Due to an oversight, release 5.8 rlog included code to write
	debugging output to stderr for invocations using the ‘-d’ option
	and a date range (e.g., ‘rlog -d 2010<2012’).

    - Criteria for avoiding read-only checks refined

	For "make check", some test cases are inhibited if the user
	running the test is not effectively blocked from writing a
	purportedly read-only file, such as when "make check" is run by
	the super user, or for certain (weird) NFS situations.

	Previously, to determine this condition, we considered only the
	operating system type, a very crude (and incomplete) proxy.
	Now, we explicitly check with a shell sequence comprising the
	umask(1) and test(1) commands, plus output-redirection.

    - Regression in ‘-zLT’ handling

	On a 64-bit x86 system, RCS 5.8 introduced a regression whereby:

	 rlog -zLT -d>2011-05-04

	would select the correct entry but display its date always with
	default (01) month and day, i.e., YYYY-01-01.  This is now fixed
	(see also tests/t320).

    - Regression in ‘ci -d -T’ handling

	RCS 5.8 introduced a regression whereby:

	  ci -l -d -T FILE

	would set the mtime of RCS/FILE,v (the comma-v file) to the
	epoch.  This is now fixed (see also tests/t810).

  - Use ‘diff --label’ instead of ‘diff -L’

	Previously, RCS used GNU diff's ‘-L’ option.  According to Paul
	Eggert (a GNU diffutils maintainer):

	  That option has been undocumented since diffutils 2.8
	  (released in March 2002) and the option is intended to
	  be replaced sometime soon with a different meaning.

	Now, RCS uses ‘diff --label’, thus immune to the planned change.

  - Miscellaneous changes
    - Make help extraction noisy (on failure)
    - Silence some compiler warnings
    - Increase coverage of "make check"

  - Documentation improvements

    - Manpage rcsintro(1) dropped

	This manpage is redundant, and (arguably) should not have been
	in section 1 in the first place.

    - Use "Invoking COMMAND" instead of "COMMAND" as node names

	This makes it easier for ‘info --usage COMMAND’ to DTRT, and
	makes GNU (info "(standards) Manual Structure Details") happy.

    - explicitly UTF-8

	This is to prepare for a (future) GNU Texinfo release that
	renders @code in a more pretty way when the encoding is UTF-8.
	If you're reading this (from the future) with such a Texinfo at
	hand, feel free to regenerate the docs in doc/ prior to install.

    - CVS is not GNU

	Previously, we incorrectly said "GNU CVS", succumbing to a
	common misunderstanding.  Now we know better.

  - TAGS file no longer distributed

	To create, configure normally and do "make TAGS".

  - New configure script option ‘--enable-coverage’

	Specifying ‘--enable-coverage’ causes ‘_Exit’ to be an alias for
	‘exit’ and CFLAGS to append ‘--coverage’ if the compiler is GCC.
	This is needed because the coverage machinery writes the .gcda
	files only on ‘exit’.

	This option is for maintainers; most people can ignore it.

  - Portability improvements
    - Use more gnulib modules
    - Use portable Makefile subst-ref variable syntax
    - Use portable shell command-output interpolation syntax
  - Maintenance tools upgraded
    - GNU Automake 1.12
    - GNU Autoconf 2.69
    - gnulib-tool (GNU gnulib 2012-06-03 16:29:00) 0.0.7432-f6c24-modified


- 5.8 | 2011-08-30

  - License now GPLv3+ (see COPYING)

  - Change in terminology: from "path" to "file name" (or "file-name")

	However, if "path" intends "search path", we say so explicitly.

  - Changes to the RCS package

    - New documentation in Info format

	On "make install", rcs.info is installed in $(infodir), with
	title "GNU RCS <VERSION>" in dircategory "Version control".
	The doc source is texinfo (released under GNU FDL 1.3), so you
	can easily create output in HTML, PDF, etc.

    - Dropped configure option: --with-diffutils

	To specify non-GNU diffutils programs diff(1) and diff3(1), name
	them using variables on the configure command-line.  See README.

    - Configuration more strict in some ways, more lax in others.

	Before, part of the configuration was done at compile time.
	Now, all of it is done by the configure script.  Here are the
	set of conditions which will cause the configure script to fail
	(with a "could not find..." message):

	 - for --enable-mailer=PROG, ‘PROG’ not absolute;
	 - for diff(1), value of env var ‘DIFF’ not absolute;
	 - diff(1) not GNU diffutils compatible;
	 - for diff3(1), value of env var ‘DIFF3’ not absolute;
	 - for ed(1), value of env var ‘ED’ not absolute;
	 - no C99-capable compiler.

	Here, "absolute" means "specified as an absolute filename".
	On the flip side, configuration no longer checks for some
	situations such as ‘sigaction’ yes, but ‘SA_SIGINFO’ no.

	Most of the portability duties are now handled by gnulib.

    - New configure option: --enable-suid[=setreuid]

	This builds RCS with setuid support (the default).  Optional
	arg ‘setreuid’ means use setreuid(2) instead of seteuid(2).

    - New configure option: --disable-mmap

	This builds RCS without mmap(2), even if available.  See README.

    - New configure option: --enable-mailer=PROG

	The feature whereby ci(1) sends mail when breaking a lock is now
	disabled by default.  To enable, specify ‘--enable-mailer=PROG’
	to the configure script.  See README.

    - New configure option: --enable-compat2

	This preponderantly unlikely to be used option allows RCS
	commands to read RCS files written by RCS 2.  See README.

    - You can "make check" prior to "make install".

	Doing "make check" automatically prepends to the ‘PATH’ env var
	the value of ‘$(abs_top_builddir)/src’, so that the programs
	co, rcsdiff, and rcsmerge can find their peers (co and merge).

	Likewise, "make installcheck" prepends ‘$(DESTDIR)$(bindir)’.

	Previously, you had to "make install" first and then arrange
	for ‘$(DESTDIR)$(bindir)’ to be on ‘PATH’ "manually".

	See tests/README for more info on the test suite.

  - Bug fixes

    - Remove all edit info when removing all revisions.

	Previously, "rcs -o" (outdating) all revisions failed to
	leave the RCS file in a consistent state; edit info (i.e.,
	log message + diff(1) output) remained for the deleted revisions.

	For example, this sequence of commands:
	  echo foo > foo
	  ci -q -i -t-desc -mHELLO foo
	  rcs -q -o1.1: foo
	  grep '@H' foo,v
	used to display "@HELLO" to stdout.

	Now, all revisions are completely removed.

    - Code no longer uses mktemp(3).

	Using mktemp(3) is a security risk.  We use mkstemp(3) now.
	Likewise, rcsfreeze.sh now uses mktemp(1).

    - Misc manpage tweaks / fixes.

	Document ‘rlog -q’; fix small merge.1 omission; add branch
	labels in rcsfile.5; say "GNU RCS <VERSION>" in footer.

  - Other changes

    - All commands accept ‘--help’ and ‘--version’.

	The help output includes an email address for bug reports.
	For continuity, option ‘-V’ is now a synonym for ‘--version’.

	Relatedly, commands no longer display usage info if given
	a bad or malformed option.  You can use ‘--help’ for that.

    - A string of all digits is now valid for author, state.

	This means you can set the author or state to, for example,
	"000000" or "42".  Previously, these would have caused a
	"invalid identifier" or "invalid symbol" error.

    - Env var RCS_MEM_LIMIT controls stdio threshold.

	For speed, RCS uses memory-based routines for files up to
	256 kilobytes, and stream-based (stdio) routines otherwise.
	You can change this threshold value by setting the environment
	variable ‘RCS_MEM_LIMIT’ to a non-negative integer, measured in
	kilobytes.  An empty ‘RCS_MEM_LIMIT’ value is silently ignored.

    - RCS can now work with files larger than 2 gigabytes.

	RCS now uses large file offsets (#define _FILE_OFFSET_BITS 64).

    - Pass-through for RCS file ‘commitid SYMBOL’ now builtin.

	Due to GNU CVS (Concurrent Versions System) using a compatible
	file format as RCS for the RCS file, you can use RCS commands
	to view and manipulate its contents.  (Note, however, the next
	NEWS item.)

	This works well enough except for a small annoyance: CVS adds a
	per-revision field called the "commitid" with an opaque (to RCS)
	symbolic value.  Previously, RCS commands would emit a warning
	"unrecognized phrases" (unless given ‘-q’ on the command-line).

	RCS commands now automatically support pass-through handling of
	‘commitid SYMBOL’ (so ‘-q’ is no longer necessary).

    - RCS file top-level grammar frozen.

	The RCS file top-level grammar is now frozen; RCS no longer
	supports pass-through operation of unrecognized key/data pairs
	(called "newphrases" in the RCS 5.7 rcsfile(5) manpage).

	To avoid painting ourselves into a corner, the grammar now
	includes a new key ‘integrity’ with @-string value, whose
	sub-grammar is not yet specified.  (We intend to keep checksums
	and other compacted redundancies in this field, for manipulation
	by the commands in a future RCS 5.x release.)  For upward
	compatability, the commands in this release do not change this
	field, although they silently read and write it (pass-through),
	if present.

    - RCS file syntax-validated earlier, completely.

	Previously, RCS file syntax was validated lazily, and trailing
	garbage was not detected (see bugfix above).  Now, a top-level
	validation is done on each access.

    - Possible to specify an empty log message with ci -m, rcs -m.

	The commands "ci -m" and "rcs -m" no longer error on an
	empty log message.  Their non-interactive behavior is now
	consistent with the interactive invocation.

	was: ci -m file < /dev/null   # use stdin to avoid error
	now: ci -m file               # works fine, like so

	Note that these commands actually store as the log message
	the string: "*** empty log message ***".

    - Date option accepts some more date-only formats

	Date format ‘YYYY-DDD’ specifies a year and a day (1-366),
	while format ‘YYYY-wWW-D’ specifies a year, an ISO week number
	(0-53, 0 is a GNU RCS extension), and a day number (1-7, for
	Monday through Sunday).

    - Changes to rcsdiff

      - New handling for option: -U N

	This arranges to output N lines of unified-diff context.
	Relatedly, the list of possible options passed to the underlying
	diff(1) appears in both "rcsdiff --help" and in the manual.

      - Refined "same-revision don't call diff" optimization

	Normally, if the two revisions specified are the same, we avoid
	calling the underlying diff(1) on the theory that it will
	produce no output.  This does not hold generally for ‘-y’
	(--side-by-side) and ‘-D’ (--ifdef), such as when the revision
	specified is by different symbolic names, so for those options
	the optimization is disabled.



- 5.7 | 1995-06-16

  Here is a brief summary of user-visible changes since 5.6.

    New options:
      ‘-kb’ supports binary files.
      ‘-T’ preserves the modification time of RCS files.
      ‘-V’ prints the version number.
      ‘-zLT’ causes RCS to use local time in working files and logs.
      ‘rcsclean -n’ outputs what rcsclean would do, without actually doing it.
      ‘rlog -N’ omits symbolic names.
    There is a new keyword ‘Name’.
    Inserted log lines now have the same prefix as the preceding ‘$Log’ line.

  Most changes for RCS version 5.7 are to fix bugs and improve portability.
  RCS now conforms to GNU configuration standards and to Posix 1003.1b-1993.

  Features new to RCS version 5.7, and possibly incompatible
  in minor ways with previous practice, include:

  - Inserted log lines now have the same prefix as the preceding ‘$Log’
    line.  E.g. if a $Log line starts with ‘// $Log’, log lines are
    prefixed with ‘// ’.  RCS still records the (now obsolescent)
    comment leader inside RCS files, but it ignores the comment leader
    unless it is emulating older RCS versions.  If you plan to access a
    file with both old and new versions of RCS, make sure its comment
    leader matches its ‘$Log’ line prefix.  For backwards compatibility
    with older versions of RCS, if the log prefix is ‘/*’ or ‘(*’
    surrounded by optional white space, inserted log lines contain ‘ *’
    instead of ‘/*’ or ‘(*’; however, this usage is obsolescent and
    should not be relied on.

  - $Log string ‘Revision’ times now use the same format as other times.

  - Log lines are now inserted even if -kk is specified; this simplifies
    merging.

  - ci's -rR option (with a nonempty R) now just specifies a revision
    number R.  In some beta versions, it also reestablished the default
    behavior of releasing a lock and removing the working file.  Now,
    only the bare -r option does this.

  - With an empty extension, any appearance of a directory named ‘RCS’
    in a pathname identifies the pathname as being that of an RCS file.
    For example, ‘a/RCS/b/c’ is now an RCS file with an empty extension.
    Formerly, ‘RCS’ had to be the last directory in the pathname.

  - rlog's -d option by default now uses exclusive time ranges.
    E.g. ‘rlog -d"<T"’ now excludes revisions whose times equal T
    exactly.  Use ‘rlog -d"<=T"’ to get the old behavior.

  - merge now takes up to three -L options, one for each input file.
    Formerly, it took at most two -L options, for the 1st and 3rd input
    files.

  - ‘rcs’ now requires at least one option; this is for future expansion.

  Other features new to RCS version 5.7 include:

  - merge and rcsmerge now pass -A, -E, and -e options to the subsidiary
    diff3.

  - rcs -kb acts like rcs -ko, except it uses binary I/O on working
    files.  This makes no difference under Posix or Unix, but it does
    matter elsewhere.  With -kb in effect, rcsmerge refuses to merge;
    this avoids common problems with CVS merging.

  - The following is for future use by GNU Emacs 19's version control
    package:

    - rcs's new -M option causes it to not send mail when you break
      somebody else's lock.  This is not meant for casual use; see
      rcs(1).

    - ci's new -i option causes an error if the RCS file already exists.
      Similarly, -j causes an error if the RCS file does not already
      exist.

  - The new keyword ‘Name’ is supported; its value is the name, if any,
    used to check out the revision.  E.g. ‘co -rN foo’ causes foo's
    $Name...$ keyword strings to end in ‘: N $’.

  - The new -zZONE option causes RCS to output dates and times using ISO
    8601 format with ZONE as the time zone, and to use ZONE as the
    default time zone for input.  Its most common use is the -zLT
    option, which causes RCS to use local time externally.  You can also
    specify foreign time zones; e.g. -z+05:30 causes RCS to use India
    time (5 hours 30 minutes east of UTC).  This option does not affect
    RCS files themselves, which always use UTC; it affects only output
    (e.g. rlog output, keyword expansion, diff -c times) and
    interpretation of options (e.g. the -d option of ci, co, and rlog).
    Bare -z restores the default behavior of UTC with no time zone
    indication, and the traditional RCS date separator ‘/’ instead of
    the ISO 8601 ‘-’.  RCSINIT may contain a -z option.  ci -k parses
    UTC offsets.

  - The new -T option of ci, co, rcs, and rcsclean preserves the
    modification time of the RCS file unless a revision is added or
    removed.  ci -T sets the RCS file's modification time to the new
    revision's time if the former precedes the latter and there is a new
    revision; otherwise, it preserves the RCS file's modification time.
    Use this option with care, as it can confuse ‘make’; see ci(1).

  - The new -N option of rlog omits symbolic names from the output.

  - A revision number that starts with ‘.’ is considered to be relative
    to the default branch (normally the trunk).  A branch number
    followed by ‘.’  stands for the last revision on that branch.

  - If someone else already holds the lock, rcs -l now asks whether you
    want to break it, instead of immediately reporting an error.

  - ci now always unlocks a revision like 3.5 if you check in a revision
    like 3.5.2.1 that is the first of a new branch of that revision.
    Formerly it was inconsistent.

  - File names may now contain tab, newline, space, and '$'.  They are
    represented in keyword strings with \t, \n, \040, and \044.  \ in a
    file name is now represented by \\ in a keyword string.

  - Identifiers may now start with a digit and (unless they are symbolic
    names) may contain ‘.’.  This permits author names like ‘john.doe’
    and ‘4tran’.

  - A bare -V option now prints the current version number.

  - rcsdiff outputs more readable context diff headers if diff -L works.

  - rcsdiff -rN -rN now suppresses needless checkout and comparison
    of identical revisions.

  - Error messages now contain the names of files to which they apply.

  - Mach style memory mapping is now supported.

  - The installation procedure now conforms to the GNU coding standards.

  - When properly configured, RCS now strictly conforms to Posix 1003.1b-1993.


- 5.6 | 1993-03-25

  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.


- 5.5 | 1991-01-04

  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 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 time zone
    boundaries.  All times are now displayed in UTC, and UTC is the
    default time zone.  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.

  - rcsclean's new -n option outputs what rcsclean would do, without
    actually doing it.

  - 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.


- 4.3 | 1989-11-18

  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.


- 3.x | ????-??-??

  Version 3 was included in the 4.3BSD distribution.



Copyright information:

   Copyright (C) 2010-2013 Thien-Thi Nguyen
   Copyright (C) 1991, 1992, 1993, 1994, 1995 Paul Eggert

   Permission is granted to anyone to make or distribute verbatim copies
   of this document as received, in any medium, provided that the
   copyright notice and this permission notice are preserved,
   thus giving the recipient permission to redistribute in turn.

   Permission is granted to distribute modified versions
   of this document, or of portions of it,
   under the above conditions, provided also that they
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