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freebsd/contrib/cvs/TODO
Peter Wemm a3b502f88f Import cvs-1.11 onto vendor branch.
2000-10-02 06:33:59 +00:00

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The "TODO" file! -*-Indented-Text-*-
22. Catch signals for cleanup when "add"ing files.
24. Insist on a log message.
(If done, this should be configurable via commitinfo or some new
config file -kingdon, Jun 1995).
30. Add "rdiff" program option to the modules database (and "diff"
too?). (perhaps should think a little harder about what this is
trying to accomplish and what the best way is -kingdon, Jul 1997).
31. Think hard about ^C recovery.
One particular issue: RCS removes the ,foo.c, file on ^C and CVS
doesn't.
38. Think hard about using RCS state information to allow one to checkin
a new vendor release without having it be accessed until it has been
integrated into the local changes.
39. Think about a version of "cvs update -j" which remembers what from
that other branch is already merged. This has pitfalls--it could
easily lead to invisible state which could confuse users very
rapidly--but having to create a tag or some such mechanism to keep
track of what has been merged is a pain. Take a look at PRCS 1.2.
PRCS 1.0 was particularly bad the way it handled the "invisible
state", but 1.2 is significantly better.
45. Consider enhancing the "rdiff" and "tag" (rtag??) command support in
the module database -- they seem hard to use since these commands
deal directly with the RCS ,v files.
49. cvs xxx commands should be able to deal with files in other
directories. I want to do a cvs add foo/bar.c.
[[ most commands now use the generic recursion processor, but not all;
this note is left here to remind me to fix the others ]]
52. SCCS has a feature that I would *love* to see in CVS, as it is very
useful. One may make a private copy of SCCS suid to a particular user,
so other users in the authentication list may check files in and out of
a project directory without mucking about with groups. Is there any
plan to provide a similar functionality to CVS? Our site (and, I'd
imagine, many other sites with large user bases) has decided against
having the user-groups feature of unix available to the users, due to
perceived administrative, technical and performance headaches. A tool
such as CVS with features that provide group-like functionality would
be a huge help.
62. Consider using revision controlled files and directories to handle the
new module format -- consider a cvs command front-end to
add/delete/modify module contents, maybe.
63. The "import" and vendor support commands (co -j) need to be documented
better.
66. Length of the CVS temporary files must be limited to 14 characters for
System-V stupid support. As well as the length on the CVS.adm files.
72. Consider re-design of the module -o, -i, -t options to use the file
system more intuitively.
73. Consider an option (in .cvsrc?) to automatically add files that are new
and specified to commit.
79. Might be nice to have some sort of interface to Sun's Translucent
(?) File System and tagged revisions.
82. Maybe the import stuff should allow an arbitrary revision to be
specified.
84. Improve the documentation about administration of the repository and
how to add/remove files and the use of symbolic links.
85. Make symbolic links a valid thing to put under version control.
Perhaps use one of the tag fields in the RCS file? Note that we
can only support symlinks that are relative and within the scope of
the sources being controlled.
92. Look into this:
After a bit of soul searching via dbx, I realized my sin was that I'd
specified "echo" as the program to call from loginfo. The commit
procedure worked fine till it hit my echo, then silently aborted
leaving the lockfiles intact. Since I needn't use the loginfo
facility, I simply removed those commands and it all works.
93. Need to think hard about release and development environments. Think
about execsets as well.
98. If diff3 bombs out (too many differences) cvs then thinks that the file
has been updated and is OK to be commited even though the file
has not yet been merged.
100. Checked out files should have revision control support. Maybe.
102. Perhaps directory modes should be propagated on all import check-ins.
Not necessarily uid/gid changes.
103. setuid/setgid on files is suspect.
104. cvs should recover nicely on unreadable files/directories.
105. cvs should have administrative tools to allow for changing permissions
and modes and what not. In particular, this would make cvs a
more attractive alternative to rdist.
107. It should be possible to specify a list of symbolic revisions to
checkout such that the list is processed in reverse order looking for
matches within the RCS file for the symbolic revision. If there is
not a match, the next symbolic rev on the list is checked, and so on,
until all symbolic revs are exhausted. This would allow one to, say,
checkout "4.0" + "4.0.3" + "4.0.3Patch1" + "4.0.3Patch2" to get the
most recent 4.x stuff. This is usually handled by just specifying the
right release_tag, but most people forget to do this.
108. If someone creates a whole new directory (i.e. adds it to the cvs
repository) and you happen to have a directory in your source farm by
the same name, when you do your cvs update -d it SILENTLY does
*nothing* to that directory. At least, I think it was silent;
certainly, it did *not* abort my cvs update, as it would have if the
same thing had happened with a file instead of a directory.
109. I had gotten pieces of the sys directory in the past but not a
complete tree. I just did something like:
cvs get *
Where sys was in * and got the message
cvs get: Executing 'sys/tools/make_links sys'
sh: sys/tools/make_links: not found
I suspect this is because I didn't have the file in question,
but I do not understand how I could fool it into getting an
error. I think a later cvs get sys seemed to work so perhaps
something is amiss in handling multiple arguments to cvs get?
113. The "cvs update" command should tee its output to a log file in ".".
(why? What is wrong with piping stdout to "tee"? -kingdon, Jun 1995)
119. When importing a directory tree that is under SCCS/RCS control,
consider an option to have import checkout the SCCS/RCS files if
necessary. (This is if someone wants to import something which
is in RCS or SCCS without preserving the history, but makes sure
they do get the latest versions. It isn't clear to me how useful
that is -kingdon, June 1996).
122. If Name_Repository fails, it currently causes CVS to die completely. It
should instead return NULL and have the caller do something reasonable
(??? -what is reasonable? I'm not sure there is a real problem here.
-kingdon, June 1996).
123. Add a flag to import to not build vendor branches for local code.
(See `importb' tests in src/sanity.sh for more details).
124. Anyway, I thought you might want to add something like the following
to the cvs man pages:
BUGS
The sum of the sizes of a module key and its contents are
limited. See ndbm(3).
126. Do an analysis to see if CVS is forgetting to close file descriptors.
Especially when committing many files (more than the open file limit
for the particular UNIX).
127. Look at *info files; they should all be quiet if the files are not
there. Should be able to point at a RCS directory and go.
130. cvs diff with no -r arguments does not need to look up the current RCS
version number since it only cares about what's in the Entries file.
This should make it much faster.
It should ParseEntries itself and access the entries list much like
Version_TS does (sticky tags and sticky options may need to be
supported here as well). Then it should only diff the things that
have the wrong time stamp (the ones that look modified).
134. Make a statement about using hard NFS mounts to your source
repository. Look into checking NULL fgets() returns with ferror() to
see if an error had occurred. (we should be checking for errors, quite
aside from NFS issues -kingdon, June 1996).
137. Some sites might want CVS to fsync() the RCS ,v file to protect
against nasty hardware errors. There is a slight performance hit with
doing so, though, so it should be configurable in the .cvsrc file.
Also, along with this, we should look at the places where CVS itself
could be a little more synchronous so as not to lose data.
[[ I've done some of this, but it could use much more ]]
138. Some people have suggested that CVS use a VPATH-like environment
variable to limit the amount of sources that need to be duplicated for
sites with giant source trees and no disk space.
141. Import should accept modules as its directory argument. If we're
going to implement this, we should think hard about how modules
might be expanded and how to handle those cases.
143. Update the documentation to show that the source repository is
something far away from the files that you work on. (People who
come from an RCS background are used to their `repository' being
_very_ close to their working directory.)
144. Have cvs checkout look for the environment variable CVSPREFIX
(or CVSMODPREFIX or some such). If it's set, then when looking
up an alias in the modules database, first look it up with the
value of CVSPREFIX attached, and then look for the alias itself.
This would be useful when you have several projects in a single
repository. You could have aliases abc_src and xyz_src and
tell people working on project abc to put "setenv CVSPREFIX abc_"
in their .cshrc file (or equivalent for other shells).
Then they could do "cvs co src" to get a copy of their src
directory, not xyz's. (This should create a directory called
src, not abc_src.)
145. After you create revision 1.1.1.1 in the previous scenario, if
you do "cvs update -r1 filename" you get revision 1.1, not
1.1.1.1. It would be nice to get the later revision. Again,
this restriction comes from RCS and is probably hard to
change in CVS. Sigh.
|"cvs update -r1 filename" does not tell RCS to follow any branches. CVS
|tries to be consistent with RCS in this fashion, so I would not change
|this. Within CVS we do have the flexibility of extending things, like
|making a revision of the form "-r1HEAD" find the most recent revision
|(branch or not) with a "1." prefix in the RCS file. This would get what
|you want maybe.
This would be very useful. Though I would prefer an option
such as "-v1" rather than "-r1HEAD". This option might be
used quite often.
146. The merging of files should be controlled via a hook so that programs
other than "rcsmerge" can be used, like Sun's filemerge or emacs's
emerge.el. (but be careful in making this work client/server--it means
doing the interactive merging at the end after the server is done).
(probably best is to have CVS do the non-interactive part and
tell the user about where the files are (.#foo.c.working and
.#foo.c.1.5 or whatever), so they can do the interactive part at
that point -kingdon, June 1996).
149. Maybe there should be an option to cvs admin that allows a user to
change the Repository/Root file with some degree of error checking?
Something like "cvs admin reposmv /old/path /new/pretty/path". Before
it does the replace it check to see that the files
/new/pretty/path/<dir>/<files> exist.
The obvious cases are where one moves the repository to another
machine or directory. But there are other cases, like where the
user might want to change from :pserver: to :ext:, use a different
server (if there are two server machines which share the
repository using a networked file system), etc.
The status quo is a bit of a mess (as of, say, CVS 1.9). It is
that the -d global option has two moderately different uses. One
is to use a totally different repository (in which case we'd
probably want to give an error if it disagreed with CVS/Root, as
CVS 1.8 and earlier did). The other is the "reposmv"
functionality above (in which the two repositories really are the
same, and we want to update the CVS/Root files). In CVS 1.9 and
1.10, -d rewrites the CVS/Root file (but not in subdirectories).
This behavior was not particularly popular and has been since
reverted.
Note also RELATIVE_REPOS in options.h; it needs to be set for
changing CVS/Root (not CVS/Repository) to be sufficient in the
case where the directory has changed.
This whole area is a rather bad pile of individual decisions which
accumulated over time, some of them probably bad decisions with
hindsight. But we didn't get into this mess overnight, and we're
not going to get out of it overnight (that is, we need to come up
with a replacement behavior, document what parts of the status
quo are deprecated, probably circulate some unofficial patches, &c).
(this item originally added 2 Feb 1992 but revised since).
150. I have a customer request for a way to specify log message per
file, non-interactively before the commit, such that a single, fully
recursive commit prompts for one commit message, and concatenates the
per file messages for each file. In short, one commit, one editor
session, log messages allowed to vary across files within the commit.
Also, the per file messages should be allowed to be written when the
files are changed, which may predate the commit considerably.
A new command seems appropriate for this. The state can be saved in the
CVS directory. I.e.,
% cvs message foo.c
Enter log message for foo.c
>> fixed an uninitialized variable
>> ^D
The text is saved as CVS/foo.c,m (or some such name) and commit
is modified to append (prepend?) the text (if found) to the log
message specified at commit time. Easy enough. (having cvs
commit be non-interactive takes care of various issues like
whether to connect to the server before or after prompting for a
message (see comment in commit.c at call to start_server). Also
would clean up the kludge for what to do with the message from
do_editor if the up-to-date check fails (see commit.c client code).
I'm not sure about the part above about having commit prompt
for an overall message--part of the point is having commit
non-interactive and somehow combining messages seems like (excess?)
hair.
Would be nice to do this so it allows users more flexibility in
specifying messages per-directory ("cvs message -l") or per-tree
("cvs message") or per-file ("cvs message foo.c"), and fixes the
incompatibility between client/server (per-tree) and
non-client/server (per-directory).
A few interesting issues with this: (1) if you do a cvs update or
some other operation which changes the working directory, do you
need to run "cvs message" again (it would, of course, bring up
the old message which you could accept)? Probably yes, after all
merging in some conflicts might change the situation. (2) How do
you change the stored messages if you change your mind before the
commit (probably run "cvs message" again, as hinted in (1))?
151. Also, is there a flag I am missing that allows replacing Ulrtx_Build
by Ultrix_build? I.E. I would like a tag replacement to be a one step
operation rather than a two step "cvs rtag -r Ulrtx_Build Ultrix_Build"
followed by "cvs rtag -d Ulrtx_Build"
152. The "cvs -n" option does not work as one would expect for all the
commands. In particular, for "commit" and "import", where one would
also like to see what it would do, without actually doing anything.
153. There should be some command (maybe I just haven't figured out
which one...) to import a source directory which is already
RCS-administered without losing all prior RCS gathered data.
Thus, it would have to examine the RCS files and choose a
starting version and branch higher than previous ones used.
(Check out rcs-to-cvs and see if it addresses this issue.)
154. When committing the modules file, a pre-commit check should be done to
verify the validity of the new modules file before allowing it to be
committed.
155. The options for "cvs history" are mutually exclusive, even though
useful queries can be done if they are not, as in specifying both
a module and a tag. A workaround is to specify the module, then
run the output through grep to only display lines that begin with
T, which are tag lines. (Better perhaps if we redesign the whole
"history" business -- check out doc/cvs.texinfo for the entire
rant.)
156. Also, how hard would it be to allow continuation lines in the
{commit,rcs,log}info files? It would probably be useful with all of
the various flags that are now available, or if somebody has a lot of
files to put into a module.
158. If I do a recursive commit and find that the same RCS file is checked
out (and modified!) in two different places within my checked-out
files (but within the realm of a single "commit"), CVS will commit the
first change, then overwrite that change with the second change. We
should catch this (typically unusual) case and issue an appropriate
diagnostic and die.
160. The checks that the commit command does should be extended to make
sure that the revision that we will lock is not already locked by
someone else. Maybe it should also lock the new revision if the old
revision was already locked by the user as well, thus moving the lock
forward after the commit.
163. The rtag/tag commands should have an option that removes the specified
tag from any file that is in the attic. This allows one to re-use a
tag (like "Mon", "Tue", ...) all the time and still have it tag the
real main-line code.
165. The "import" command will create RCS files automatically, but will
screw-up when trying to create long file names on short file name
file systems. Perhaps import should be a bit more cautious.
166. There really needs to be a "Getting Started" document which describes
some of the new CVS philosophies. Folks coming straight from SCCS or
RCS might be confused by "cvs import". Also need to explain:
- How one might setup their $CVSROOT
- What all the tags mean in an "import" command
- Tags are important; revision numbers are not
170. Is there an "info" file that can be invoked when a file is checked out, or
updated ? What I want to do is to advise users, particularly novices, of
the state of their working source whenever they check something out, as
a sanity check.
For example, I've written a perl script which tells you what branch you're
on, if any. Hopefully this will help guard against mistaken checkins to
the trunk, or to the wrong branch. I suppose I can do this in
"commitinfo", but it'd be nice to advise people before they edit their
files.
It would also be nice if there was some sort of "verboseness" switch to
the checkout and update commands that could turn this invocation of the
script off, for mature users.
173. We have a tagged branch in CVS. How do we get the version of that branch
(for an entire directory) that corresponds to the files on that branch on a
certain day? I'd like to specify BOTH -r and -D to 'cvs checkout', but I
can't. It looks like I can only specify the date for the main line (as
opposed to any branches). True? Any workarounds to get what I need?
174. I would like to see "cvs release" modified so that it only removes files
which are known to CVS - all the files in the repository, plus those which
are listed in .cvsignore. This way, if you do leave something valuable in
a source tree you can "cvs release -d" the tree and your non-CVS goodies
are still there. If a user is going to leave non-CVS files in their source
trees, they really should have to clean them up by hand.
175. And, in the feature request department, I'd dearly love a command-line
interface to adding a new module to the CVSROOT/modules file.
176. If you use the -i flag in the modules file, you can control access
to source code; this is a Good Thing under certain circumstances. I
just had a nasty thought, and on experiment discovered that the
filter specified by -i is _not_ run before a cvs admin command; as
this allows a user to go behind cvs's back and delete information
(cvs admin -o1.4 file) this seems like a serious problem.
177. We've got some external vendor source that sits under a source code
hierarchy, and when we do a cvs update, it gets wiped out because
its tag is different from the "main" distribution. I've tried to
use "-I" to ignore the directory, as well as .cvsignore, but this
doesn't work.
179. "cvs admin" does not log its actions with loginfo, nor does it check
whether the action is allowed with commitinfo. It should.
180. "cvs edit" should show you who is already editing the files,
probably (that is, do "cvs editors" before executing, or some
similar result). (But watch out for what happens if the network
is down!).
182. There should be a way to show log entries corresponding to
changes from tag "foo" to tag "bar". "cvs log -rfoo:bar" doesn't cut
it, because it erroneously shows the changes associated with the
change from the revision before foo to foo. I'm not sure that is ever
a useful or logical behavior ("cvs diff -r foo -r bar" gets this
right), but is compatibility an issue? See
http://www.cyclic.com/cvs/unoff-log.txt for an unofficial patch.
183. "cvs status" should report on Entries.Static flag and CVS/Tag (how?
maybe a "cvs status -d" to give directory status?). There should also
be more documentation of how these get set and how/when to re-set them.
184. Would be nice to implement the FreeBSD MD5-based password hash
algorithm in pserver. For more info see "6.1. DES, MD5, and Crypt" in
the FreeBSD Handbook, and src/lib/libcrypt/crypt.c in the FreeBSD
sources. Certainly in the context of non-unix servers this algorithm
makes more sense than the traditional unix crypt() algorithm, which
suffers from export control problems.
185. A frequent complaint is that keyword expansion causes conflicts
when merging from one branch to another. The first step is
documenting CVS's existing features in this area--what happens with
various -k options in various places? The second step is thinking
about whether there should be some new feature and if so how it should
be designed. For example, here is one thought:
rcs' co command needs a new -k option. The new option should expand
$Log entries without expanding $Revision entries. This would
allow cvs to use rcsmerge in such a way that joining branches into
main lines would neither generate extra collisions on revisions nor
drop log lines.
The details of this are out of date (CVS no longer invokes "co", and
any changes in this area would be done by bypassing RCS rather than
modifying it), but even as to the general idea, I don't have a clear
idea about whether it would be good (see what I mean about the need
for better documentation? I work on CVS full-time, and even I don't
understand the state of the art on this subject).
186. There is a frequent discussion of multisite features.
* There may be some overlap with the client/server CVS, which is good
especially when there is a single developer at each location. But by
"multisite" I mean something in which each site is more autonomous, to
one extent or another.
* Vendor branches are the closest thing that CVS currently has for
multisite features. They have fixable drawbacks (such as poor
handling of added and removed files), and more fundamental drawbacks
(when you import a vendor branch, you are importing a set of files,
not importing any knowledge of their version history outside the
current repository).
* One approach would be to require checkins (or other modifications to
the repository) to succeed at a write quorum of sites (51%) before
they are allowed to complete. To work well, the network should be
reliable enough that one can typically get to that many sites. When a
server which has been out of touch reconnects, it would want to update
its data before doing anything else. Any of the servers can service
all requests locally, except perhaps for a check that they are
up-to-date. The way this differs from a run-of-the-mill distributed
database is that if one only allows reversible operations via this
mechanism (exclude "cvs admin -o", "cvs tag -d", &c), then each site
can back up the others, such that failures at one site, including
something like deleting all the sources, can be recovered from. Thus
the sites need not trust each other as much as for many shared
databases, and the system may be resilient to many types of
organizational failures. Sometimes I call this design the
"CVScluster" design.
* Another approach is a master/slave one. Checkins happen at the
master site, and slave sites need to check whether their local
repository is up to date before relying on its information.
* Another approach is to have each site own a particular branch. This
one is the most tolerant of flaky networks; if checkins happen at each
site independently there is no particular problem. The big question
is whether merges happen only manually, as with existing CVS branches,
or whether there is a feature whereby there are circumstances in which
merges from one branch to the other happen automatically (for example,
the case in which the branches have not diverged). This might be a
legitimate question to ask even quite aside from multisite features.
187. Might want to separate out usage error messages and help
messages. The problem now is that if you specify an invalid option,
for example, the error message is lost among all the help text. In
the new regime, the error message would be followed by a one-line
message directing people to the appropriate help option ("cvs -H
<command>" or "cvs --help-commands" or whatever, according to the
situation). I'm not sure whether this change would be controversial
(as defined in HACKING), so there might be a need for further
discussion or other actions other than just coding.
188. Option parsing and .cvsrc has at least one notable limitation.
If you want to set a global option only for some CVS commands, there
is no way to do it (for example, if one wants to set -q only for
"rdiff"). I am told that the "popt" package from RPM
(http://www.rpm.org) could solve this and other problems (for example,
if the syntax of option stuff in .cvsrc is similar to RPM, that would
be great from a user point of view). It would at least be worth a
look (it also provides a cleaner API than getopt_long).
Another issue which may or may not be related is the issue of
overriding .cvsrc from the command line. The cleanest solution might
be to have options in mutually exclusive sets (-l/-R being a current
example, but --foo/--no-foo is a better way to name such options). Or
perhaps there is some better solution.
189. Renaming files and directories is a frequently discussed topic.
Some of the problems with the status quo:
a. "cvs annotate" cannot operate on both the old and new files in a
single run. You need to run it twice, once for the new name and once
for the old name.
b. "cvs diff" (or "cvs diff -N") shows a rename as a removal of the
old file and an addition of the new one. Some people would like to
see the differences between the file contents (but then how would we
indicate the fact that the file has been renamed? Certainly the
notion that "patch(1)" has of renames is as a removal and addition).
c. "cvs log" should be able to show the changes between two
tags/dates, even in the presence of adds/removes/renames (I'm not sure
what the status quo is on this; see also item #182).
d. Renaming directories is way too hard.
Implementations:
It is perhaps premature to try to design implementation details
without answering some of the above questions about desired behaviors
but several general implementations get mentioned.
i. No fundamental changes (for example, a "cvs rename" command which
operated on directories could still implement the current recommended
practice for renaming directories, which is to rename each of the
files contained therein via an add and a remove). One thing to note
that the status quo gets right is proper merges, even with adds and
removals (Well, mostly right at least. There are a *LOT* of different
cases; see the testsuite for some of them).
ii. Rename database. In this scheme the files in the repository
would have some arbitrary name, and then a separate rename database
would indicate the current correspondence between the filename in the
working directory and the actual storage. As far as I know this has
never been designed in detail for CVS.
iii. A modest change in which the RCS files would contain some
information such as "renamed from X" or "renamed to Y". That is, this
would be generally similar to the log messages which are suggested
when one renames via an add and a removal, but would be
computer-parseable. I don't think anyone has tried to flesh out any
details here either.
It is interesting to note that in solution ii. version numbers in the
"new file" start where the "old file" left off, while in solutions
i. and iii., version numbers restart from 1.1 each time a file is
renamed. Except perhaps in the case where we rename a file from foo
to bar and then back to foo. I'll shut up now.
Regardless of the method we choose, we need to address how renames
affect existing CVS behaviors. For example, what happens when you
rename a file on a branch but not the trunk and then try to merge the
two? What happens when you rename a file on one branch and delete it
on another and try to merge the two?
Ideally, we'd come up with a way to parameterize the problem and
simply write up a lookup table to determine the correct behavior.
190. The meaning of the -q and -Q global options is very ad hoc;
there is no clear definition of which messages are suppressed by them
and which are not. Here is a classification of the current meanings
of -q; I don't know whether anyone has done a similar investigation of
-Q:
a. The "warm fuzzies" printed upon entering each directory (for
example, "cvs update: Updating sdir"). The need for these messages
may be decreased now that most of CVS uses ->fullname instead of
->file in messages (a project which is *still* not 100% complete,
alas). However, the issue of whether CVS can offer status as it
runs is an important one. Of course from the command line it is
hard to do this well and one ends up with options like -q. But
think about emacs, jCVS, or other environments which could flash you
the latest status line so you can see whether the system is working
or stuck.
b. Other cases where the message just offers information (rather
than an error) and might be considered unnecessarily verbose. These
have a certain point to them, although it isn't really clear whether
it should be the same option as the warm fuzzies or whether it is
worth the conceptual hair:
add.c: scheduling %s `%s' for addition (may be an issue)
modules.c: %s %s: Executing '%s' (I can see how that might be noise,
but...)
remove.c: scheduling `%s' for removal (analogous to the add.c one)
update.c: Checking out %s (hmm, that message is a bit on the noisy side...)
(but the similar message in annotate is not affected by -q).
c. Suppressing various error messages. This is almost surely
bogus.
commit.c: failed to remove tag `%s' from `%s' (Questionable.
Rationale might be that we already printed another message
elsewhere but why would it be necessary to avoid
the extra message in such an uncommon case?)
commit.c: failed to commit dead revision for `%s' (likewise)
remove.c: file `%s' still in working directory (see below about rm
-f analogy)
remove.c: nothing known about `%s' (looks dubious to me, especially in
the case where the user specified it explicitly).
remove.c: removed `%s' (seems like an obscure enough case that I fail
to see the appeal of being cryptically concise here).
remove.c: file `%s' already scheduled for removal (now it is starting
to look analogous to the infamous rm -f option).
rtag.c: cannot find tag `%s' in `%s' (more rm -f like behavior)
rtag.c: failed to remove tag `%s' from `%s' (ditto)
tag.c: failed to remove tag %s from %s (see above about whether RCS_*
has already printed an error message).
tag.c: couldn't tag added but un-commited file `%s' (more rm -f
like behavior)
tag.c: skipping removed but un-commited file `%s' (ditto)
tag.c: cannot find revision control file for `%s' (ditto, but at first
glance seems even worse, as this would seem to be a "can't happen"
condition)
191. Storing RCS files, especially binary files, takes rather more
space than it could, typically.
- The virtue of the status quo is that it is simple to implement.
Of course it is also simplest in terms of dealing with compatibility.
- Just storing the revisions as separate gzipped files is a common
technique. It also is pretty simple (no new algorithms, CVS
already has zlib around). Of course for some files (such as files
which are already compressed) the gzip step won't help, but
something which can at least sometimes avoid rewriting the entire
RCS file for each new revision would, I would think, be a big
speedup for large files.
- Josh MacDonald has written a tool called xdelta which produces
differences (that is, sufficient information to transform the old
to the new) which looks for common sequences of bytes, like RCS
currently does, but which is not based on lines. This seems to do
quite well for some kinds of files (e.g. FrameMaker documents,
text files), and not as well for others (anything which is already
compressed, executables). xdelta 1.10 also is faster than GNU diff.
- Karl Fogel has thought some about using a difference technique
analogous to fractal compression (see the comp.compression FAQ for
more on fractal compression, including at least one patent to
watch for; I don't know how analogous Karl's ideas are to the
techniques described there).
- Quite possibly want some documented interface by which a site can
plug in their choice of external difference programs (with the
ability to choose the program based on filename, magic numbers,
or some such).
192. "cvs update" using an absolute pathname does not work if the
working directory is not a CVS-controlled directory with the correct
CVSROOT. For example, the following will fail:
cd /tmp
cvs -d /repos co foo
cd /
cvs update /tmp/foo
It is possible to read the CVSROOT from the administrative files in
the directory specified by the absolute pathname argument to update.
In that case, the last command above would be equivalent to:
cd /tmp/foo
cvs update .
This can be problematic, however, if we ask CVS to update two
directories with different CVSROOTs. Currently, CVS has no way of
changing CVSROOT mid-stream. Consider the following:
cd /tmp
cvs -d /repos1 co foo
cvs -d /repos2 co bar
cd /
cvs update /tmp/foo /tmp/bar
To make that example work, we need to think hard about:
- where and when CVSROOT-related variables get set
- who caches said variables for later use
- how the remote protocol should be extended to handle sending a new
repository mid-stream
- how the client should maintain connections to a variety of servers
in a single invocation.
Because those issues are hairy, I suspect that having a change in
CVSROOT be an error would be a better move.
193. The client relies on timestamps to figure out whether a file is
(maybe) modified. If something goes awry, then it ends up sending
entire files to the server to be checked, and this can be quite slow
especially over a slow network. A couple of things that can happen:
(a) other programs, like make, use timestamps, so one ends up needing
to do "touch foo" and otherwise messing with timestamps, (b) changing
the timezone offset (e.g. summer vs. winter or moving a machine)
should work on unix, but there may be problems with non-unix.
Possible solutions:
a. Store a checksum for each file in CVS/Entries or some such
place. What to do about hash collisions is interesting: using a
checksum, like MD5, large enough to "never" have collisions
probably works in practice (of course, if there is a collision then
all hell breaks loose because that code path was not tested, but
given the tiny, tiny probability of that I suppose this is only an
aesthetic issue).
b. I'm not thinking of others, except storing the whole file in
CVS/Base, and I'm sure using twice the disk space would be
unpopular.
194. CVS does not separate the "metadata" from the actual revision
history; it stores them both in the RCS files. Metadata means tags
and header information such as the number of the head revision.
Storing the metadata separately could speed up "cvs tag" enormously,
which is a big problem for large repositories. It could also probably
make CVS's locking much less in the way (see comment in do_recursion
about "two-pass design").
195. Many people using CVS over a slow link are interested in whether
the remote protocol could be any more efficient with network
bandwidth. This item is about one aspect of that--how the server
sends a new version of a file the client has a different version of,
or vice versa.
a. Cases in which the status quo already sends a diff. For most text
files, this is probably already close to optimal. For binary files,
and anomalous (?) text files (e.g. those in which it would help to do
moves, as well as adds and deletes), it might be worth looking into other
difference algorithms (see item #191).
b. Cases in which the status quo does not send a diff (e.g. "cvs
commit").
b1. With some frequency, people suggest rsync or a similar algorithm
(see ftp://samba.anu.edu.au/pub/rsync/). This could speed things up,
and in some ways involves the most minimal changes to the default CVS
paradigm. There are some downsides though: (1) there is an extra
network turnaround, (2) the algorithm needs to transmit some data to
discover what difference type programs can discover locally (although
this is only about 1% of the size of the files).
b2. If one is willing to require that users use "cvs edit" before
editing a file on the client side (in some cases, a development
environment like emacs can make this fairly easy), then the Modified
request in the protocol could be extended to allow the client to just
send differences instead of entire files. In the degenerate case
(e.g. "cvs diff" without arguments) the required network traffic is
reduced to zero, and the client need not even contact the server.
196. Using a CVSROOT with a trailing slash will confuse CVS. I think
we need to add a call to strip_trailing_slashes in root.c
(parse_cvsroot), but I haven't considered all of the ramifications.
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