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This is cvsclient.info, produced by makeinfo version 4.0 from cvsclient.texi. INFO-DIR-SECTION Programming START-INFO-DIR-ENTRY * cvsclient: (cvsclient). The CVS client/server protocol. END-INFO-DIR-ENTRY File: cvsclient.info, Node: Responses, Next: Text tags, Prev: Response pathnames, Up: Protocol Responses ========= Here are the responses: `Valid-requests REQUEST-LIST \n' Indicate what requests the server will accept. REQUEST-LIST is a space separated list of tokens. If the server supports sending patches, it will include `update-patches' in this list. The `update-patches' request does not actually do anything. `Checked-in PATHNAME \n' Additional data: New Entries line, \n. This means a file PATHNAME has been successfully operated on (checked in, added, etc.). name in the Entries line is the same as the last component of PATHNAME. `New-entry PATHNAME \n' Additional data: New Entries line, \n. Like `Checked-in', but the file is not up to date. `Updated PATHNAME \n' Additional data: New Entries line, \n, mode, \n, file transmission. A new copy of the file is enclosed. This is used for a new revision of an existing file, or for a new file, or for any other case in which the local (client-side) copy of the file needs to be updated, and after being updated it will be up to date. If any directory in pathname does not exist, create it. This response is not used if `Created' and `Update-existing' are supported. `Created PATHNAME \n' This is just like `Updated' and takes the same additional data, but is used only if no `Entry', `Modified', or `Unchanged' request has been sent for the file in question. The distinction between `Created' and `Update-existing' is so that the client can give an error message in several cases: (1) there is a file in the working directory, but not one for which `Entry', `Modified', or `Unchanged' was sent (for example, a file which was ignored, or a file for which `Questionable' was sent), (2) there is a file in the working directory whose name differs from the one mentioned in `Created' in ways that the client is unable to use to distinguish files. For example, the client is case-insensitive and the names differ only in case. `Update-existing PATHNAME \n' This is just like `Updated' and takes the same additional data, but is used only if a `Entry', `Modified', or `Unchanged' request has been sent for the file in question. This response, or `Merged', indicates that the server has determined that it is OK to overwrite the previous contents of the file specified by PATHNAME. Provided that the client has correctly sent `Modified' or `Is-modified' requests for a modified file, and the file was not modified while CVS was running, the server can ensure that a user's modifications are not lost. `Merged PATHNAME \n' This is just like `Updated' and takes the same additional data, with the one difference that after the new copy of the file is enclosed, it will still not be up to date. Used for the results of a merge, with or without conflicts. It is useful to preserve an copy of what the file looked like before the merge. This is basically handled by the server; before sending `Merged' it will send a `Copy-file' response. For example, if the file is `aa' and it derives from revision 1.3, the `Copy-file' response will tell the client to copy `aa' to `.#aa.1.3'. It is up to the client to decide how long to keep this file around; traditionally clients have left it around forever, thus letting the user clean it up as desired. But another answer, such as until the next commit, might be preferable. `Rcs-diff PATHNAME \n' This is just like `Updated' and takes the same additional data, with the one difference that instead of sending a new copy of the file, the server sends an RCS change text. This change text is produced by `diff -n' (the GNU diff `-a' option may also be used). The client must apply this change text to the existing file. This will only be used when the client has an exact copy of an earlier revision of a file. This response is only used if the `update' command is given the `-u' argument. `Patched PATHNAME \n' This is just like `Rcs-diff' and takes the same additional data, except that it sends a standard patch rather than an RCS change text. The patch is produced by `diff -c' for CVS 1.6 and later (see POSIX.2 for a description of this format), or `diff -u' for previous versions of CVS; clients are encouraged to accept either format. Like `Rcs-diff', this response is only used if the `update' command is given the `-u' argument. The `Patched' response is deprecated in favor of the `Rcs-diff' response. However, older clients (CVS 1.9 and earlier) only support `Patched'. `Mode MODE \n' This MODE applies to the next file mentioned in `Checked-in'. `Mode' is a file update modifying response as described in *Note Response intro::. `Mod-time TIME \n' Set the modification time of the next file sent to TIME. `Mod-time' is a file update modifying response as described in *Note Response intro::. The TIME is in the format specified by RFC822 as modified by RFC1123. The server may specify any timezone it chooses; clients will want to convert that to their own timezone as appropriate. An example of this format is: 26 May 1997 13:01:40 -0400 There is no requirement that the client and server clocks be synchronized. The server just sends its recommendation for a timestamp (based on its own clock, presumably), and the client should just believe it (this means that the time might be in the future, for example). If the server does not send `Mod-time' for a given file, the client should pick a modification time in the usual way (usually, just let the operating system set the modification time to the time that the CVS command is running). `Checksum CHECKSUM\n' The CHECKSUM applies to the next file sent (that is, `Checksum' is a file update modifying response as described in *Note Response intro::). In the case of `Patched', the checksum applies to the file after being patched, not to the patch itself. The client should compute the checksum itself, after receiving the file or patch, and signal an error if the checksums do not match. The checksum is the 128 bit MD5 checksum represented as 32 hex digits (MD5 is described in RFC1321). This response is optional, and is only used if the client supports it (as judged by the `Valid-responses' request). `Copy-file PATHNAME \n' Additional data: NEWNAME \n. Copy file PATHNAME to NEWNAME in the same directory where it already is. This does not affect `CVS/Entries'. This can optionally be implemented as a rename instead of a copy. The only use for it which currently has been identified is prior to a `Merged' response as described under `Merged'. Clients can probably assume that is how it is being used, if they want to worry about things like how long to keep the NEWNAME file around. `Removed PATHNAME \n' The file has been removed from the repository (this is the case where cvs prints `file foobar.c is no longer pertinent'). `Remove-entry PATHNAME \n' The file needs its entry removed from `CVS/Entries', but the file itself is already gone (this happens in response to a `ci' request which involves committing the removal of a file). `Set-static-directory PATHNAME \n' This instructs the client to set the `Entries.Static' flag, which it should then send back to the server in a `Static-directory' request whenever the directory is operated on. PATHNAME ends in a slash; its purpose is to specify a directory, not a file within a directory. `Clear-static-directory PATHNAME \n' Like `Set-static-directory', but clear, not set, the flag. `Set-sticky PATHNAME \n' Additional data: TAGSPEC \n. Tell the client to set a sticky tag or date, which should be supplied with the `Sticky' request for future operations. PATHNAME ends in a slash; its purpose is to specify a directory, not a file within a directory. The client should store TAGSPEC and pass it back to the server as-is, to allow for future expansion. The first character of TAGSPEC is `T' for a tag, `D' for a date, or something else for future expansion. The remainder of TAGSPEC contains the actual tag or date. `Clear-sticky PATHNAME \n' Clear any sticky tag or date set by `Set-sticky'. `Template PATHNAME \n' Additional data: file transmission (note: compressed file transmissions are not supported). PATHNAME ends in a slash; its purpose is to specify a directory, not a file within a directory. Tell the client to store the file transmission as the template log message, and then use that template in the future when prompting the user for a log message. `Set-checkin-prog DIR \n' Additional data: PROG \n. Tell the client to set a checkin program, which should be supplied with the `Checkin-prog' request for future operations. `Set-update-prog DIR \n' Additional data: PROG \n. Tell the client to set an update program, which should be supplied with the `Update-prog' request for future operations. `Notified PATHNAME \n' Indicate to the client that the notification for PATHNAME has been done. There should be one such response for every `Notify' request; if there are several `Notify' requests for a single file, the requests should be processed in order; the first `Notified' response pertains to the first `Notify' request, etc. `Module-expansion PATHNAME \n' Return a file or directory which is included in a particular module. PATHNAME is relative to cvsroot, unlike most pathnames in responses. PATHNAME should be used to look and see whether some or all of the module exists on the client side; it is not necessarily suitable for passing as an argument to a `co' request (for example, if the modules file contains the `-d' option, it will be the directory specified with `-d', not the name of the module). `Wrapper-rcsOption PATTERN -k 'OPTION' \n' Transmit to the client a filename pattern which implies a certain keyword expansion mode. The PATTERN is a wildcard pattern (for example, `*.exe'. The OPTION is `b' for binary, and so on. Note that although the syntax happens to resemble the syntax in certain CVS configuration files, it is more constrained; there must be exactly one space between PATTERN and `-k' and exactly one space between `-k' and `'', and no string is permitted in place of `-k' (extensions should be done with new responses, not by extending this one, for graceful handling of `Valid-responses'). `M TEXT \n' A one-line message for the user. Note that the format of TEXT is not designed for machine parsing. Although sometimes scripts and clients will have little choice, the exact text which is output is subject to vary at the discretion of the server and the example output given in this document is just that, example output. Servers are encouraged to use the `MT' response, and future versions of this document will hopefully standardize more of the `MT' tags; see *Note Text tags::. `Mbinary \n' Additional data: file transmission (note: compressed file transmissions are not supported). This is like `M', except the contents of the file transmission are binary and should be copied to standard output without translation to local text file conventions. To transmit a text file to standard output, servers should use a series of `M' requests. `E TEXT \n' Same as `M' but send to stderr not stdout. `F \n' Flush stderr. That is, make it possible for the user to see what has been written to stderr (it is up to the implementation to decide exactly how far it should go to ensure this). `MT TAGNAME DATA \n' This response provides for tagged text. It is similar to SGML/HTML/XML in that the data is structured and a naive application can also make some sense of it without understanding the structure. The syntax is not SGML-like, however, in order to fit into the CVS protocol better and (more importantly) to make it easier to parse, especially in a language like perl or awk. The TAGNAME can have several forms. If it starts with `a' to `z' or `A' to `Z', then it represents tagged text. If the implementation recognizes TAGNAME, then it may interpret DATA in some particular fashion. If the implementation does not recognize TAGNAME, then it should simply treat DATA as text to be sent to the user (similar to an `M' response). There are two tags which are general purpose. The `text' tag is similar to an unrecognized tag in that it provides text which will ordinarily be sent to the user. The `newline' tag is used without DATA and indicates that a newline will ordinarily be sent to the user (there is no provision for embedding newlines in the DATA of other tagged text responses). If TAGNAME starts with `+' it indicates a start tag and if it starts with `-' it indicates an end tag. The remainder of TAGNAME should be the same for matching start and end tags, and tags should be nested (for example one could have tags in the following order `+bold' `+italic' `text' `-italic' `-bold' but not `+bold' `+italic' `text' `-bold' `-italic'). A particular start and end tag may be documented to constrain the tagged text responses which are valid between them. Note that if DATA is present there will always be exactly one space between TAGNAME and DATA; if there is more than one space, then the spaces beyond the first are part of DATA. Here is an example of some tagged text responses. Note that there is a trailing space after `Checking in' and `initial revision:' and there are two trailing spaces after `<--'. Such trailing spaces are, of course, part of DATA. MT +checking-in MT text Checking in MT fname gz.tst MT text ; MT newline MT rcsfile /home/kingdon/zwork/cvsroot/foo/gz.tst,v MT text <-- MT fname gz.tst MT newline MT text initial revision: MT init-rev 1.1 MT newline MT text done MT newline MT -checking-in If the client does not support the `MT' response, the same responses might be sent as: M Checking in gz.tst; M /home/kingdon/zwork/cvsroot/foo/gz.tst,v <-- gz.tst M initial revision: 1.1 M done For a list of specific tags, see *Note Text tags::. `error ERRNO-CODE ` ' TEXT \n' The command completed with an error. ERRNO-CODE is a symbolic error code (e.g. `ENOENT'); if the server doesn't support this feature, or if it's not appropriate for this particular message, it just omits the errno-code (in that case there are two spaces after `error'). Text is an error message such as that provided by strerror(), or any other message the server wants to use. The TEXT is like the `M' response, in the sense that it is not particularly intended to be machine-parsed; servers may wish to print an error message with `MT' responses, and then issue a `error' response without TEXT (although it should be noted that `MT' currently has no way of flagging the output as intended for standard error, the way that the `E' response does). `ok \n' The command completed successfully. File: cvsclient.info, Node: Text tags, Next: Example, Prev: Responses, Up: Protocol Tags for the MT tagged text response ==================================== The `MT' response, as described in *Note Responses::, offers a way for the server to send tagged text to the client. This section describes specific tags. The intention is to update this section as servers add new tags. In the following descriptions, `text' and `newline' tags are omitted. Such tags contain information which is intended for users (or to be discarded), and are subject to change at the whim of the server. To avoid being vulnerable to such whim, clients should look for the tags listed here, not `text', `newline', or other tags. The following tag means to indicate to the user that a file has been updated. It is more or less redundant with the `Created' and `Update-existing' responses, but we don't try to specify here whether it occurs in exactly the same circumstances as `Created' and `Update-existing'. The NAME is the pathname of the file being updated relative to the directory in which the command is occurring (that is, the last `Directory' request which is sent before the command). MT +updated MT fname NAME MT -updated The `importmergecmd' tag is used when doing an import which has conflicts. The client can use it to report how to merge in the newly imported changes. The COUNT is the number of conflicts. The newly imported changes can be merged by running the following command: cvs checkout -j TAG1 -j TAG2 REPOSITORY MT +importmergecmd MT conflicts COUNT MT mergetag1 TAG1 MT mergetag2 TAG2 MT repository REPOSITORY MT -importmergecmd File: cvsclient.info, Node: Example, Next: Requirements, Prev: Text tags, Up: Protocol Example ======= Here is an example; lines are prefixed by `C: ' to indicate the client sends them or `S: ' to indicate the server sends them. The client starts by connecting, sending the root, and completing the protocol negotiation. In actual practice the lists of valid responses and requests would be longer. C: Root /u/cvsroot C: Valid-responses ok error Checked-in M E C: valid-requests S: Valid-requests Root Directory Entry Modified Argument Argumentx ci co S: ok C: UseUnchanged The client wants to check out the `supermunger' module into a fresh working directory. Therefore it first expands the `supermunger' module; this step would be omitted if the client was operating on a directory rather than a module. C: Argument supermunger C: Directory . C: /u/cvsroot C: expand-modules The server replies that the `supermunger' module expands to the directory `supermunger' (the simplest case): S: Module-expansion supermunger S: ok The client then proceeds to check out the directory. The fact that it sends only a single `Directory' request which specifies `.' for the working directory means that there is not already a `supermunger' directory on the client. C: Argument -N C: Argument supermunger C: Directory . C: /u/cvsroot C: co The server replies with the requested files. In this example, there is only one file, `mungeall.c'. The `Clear-sticky' and `Clear-static-directory' requests are sent by the current implementation but they have no effect because the default is for those settings to be clear when a directory is newly created. S: Clear-sticky supermunger/ S: /u/cvsroot/supermunger/ S: Clear-static-directory supermunger/ S: /u/cvsroot/supermunger/ S: E cvs server: Updating supermunger S: M U supermunger/mungeall.c S: Created supermunger/ S: /u/cvsroot/supermunger/mungeall.c S: /mungeall.c/1.1/// S: u=rw,g=r,o=r S: 26 S: int mein () { abort (); } S: ok The current client implementation would break the connection here and make a new connection for the next command. However, the protocol allows it to keep the connection open and continue, which is what we show here. After the user modifies the file and instructs the client to check it back in. The client sends arguments to specify the log message and file to check in: C: Argument -m C: Argument Well, you see, it took me hours and hours to find C: Argumentx this typo and I searched and searched and eventually C: Argumentx had to ask John for help. C: Argument mungeall.c It also sends information about the contents of the working directory, including the new contents of the modified file. Note that the user has changed into the `supermunger' directory before executing this command; the top level directory is a user-visible concept because the server should print filenames in `M' and `E' responses relative to that directory. C: Directory . C: /u/cvsroot/supermunger C: Entry /mungeall.c/1.1/// C: Modified mungeall.c C: u=rw,g=r,o=r C: 26 C: int main () { abort (); } And finally, the client issues the checkin command (which makes use of the data just sent): C: ci And the server tells the client that the checkin succeeded: S: M Checking in mungeall.c; S: E /u/cvsroot/supermunger/mungeall.c,v <-- mungeall.c S: E new revision: 1.2; previous revision: 1.1 S: E done S: Mode u=rw,g=r,o=r S: Checked-in ./ S: /u/cvsroot/supermunger/mungeall.c S: /mungeall.c/1.2/// S: ok File: cvsclient.info, Node: Requirements, Next: Obsolete, Prev: Example, Up: Protocol Required versus optional parts of the protocol ============================================== The following are part of every known implementation of the CVS protocol (except obsolete, pre-1.5, versions of CVS) and it is considered reasonable behavior to completely fail to work if you are connected with an implementation which attempts to not support them. Requests: `Root', `Valid-responses', `valid-requests', `Directory', `Entry', `Modified', `Unchanged', `Argument', `Argumentx', `ci', `co', `update'. Responses: `ok', `error', `Valid-requests', `Checked-in', `Updated', `Merged', `Removed', `M', `E'. A server need not implement `Repository', but in order to interoperate with CVS 1.5 through 1.9 it must claim to implement it (in `Valid-requests'). The client will not actually send the request. File: cvsclient.info, Node: Obsolete, Prev: Requirements, Up: Protocol Obsolete protocol elements ========================== This section briefly describes protocol elements which are obsolete. There is no attempt to document them in full detail. There was a `Repository' request which was like `Directory' except it only provided REPOSITORY, and the local directory was assumed to be similarly named. If the `UseUnchanged' request was not sent, there was a `Lost' request which was sent to indicate that a file did not exist in the working directory, and the meaning of sending `Entries' without `Lost' or `Modified' was different. All current clients (CVS 1.5 and later) will send `UseUnchanged' if it is supported. File: cvsclient.info, Node: Protocol Notes, Prev: Protocol, Up: Top Notes on the Protocol ********************* A number of enhancements are possible. Also see the file TODO in the CVS source distribution, which has further ideas concerning various aspects of CVS, some of which impact the protocol. Similarly, the `http://www.cvshome.org' site, in particular the `Development' pages. * The `Modified' request could be speeded up by sending diffs rather than entire files. The client would need some way to keep the version of the file which was originally checked out; probably requiring the use of "cvs edit" in this case is the most sensible course (the "cvs edit" could be handled by a package like VC for emacs). This would also allow local operation of `cvs diff' without arguments. * The fact that `pserver' requires an extra network turnaround in order to perform authentication would be nice to avoid. This relates to the issue of reporting errors; probably the clean solution is to defer the error until the client has issued a request which expects a response. To some extent this might relate to the next item (in terms of how easy it is to skip a whole bunch of requests until we get to one that expects a response). I know that the kerberos code doesn't wait in this fashion, but that probably can cause network deadlocks and perhaps future problems running over a transport which is more transaction oriented than TCP. On the other hand I'm not sure it is wise to make the client conduct a lengthy upload only to find there is an authentication failure. * The protocol uses an extra network turnaround for protocol negotiation (`valid-requests'). It might be nice to avoid this by having the client be able to send requests and tell the server to ignore them if they are unrecognized (different requests could produce a fatal error if unrecognized). To do this there should be a standard syntax for requests. For example, perhaps all future requests should be a single line, with mechanisms analogous to `Argumentx', or several requests working together, to provide greater amounts of information. Or there might be a standard mechanism for counted data (analogous to that used by `Modified') or continuation lines (like a generalized `Argumentx'). It would be useful to compare what HTTP is planning in this area; last I looked they were contemplating something called Protocol Extension Protocol but I haven't looked at the relevant IETF documents in any detail. Obviously, we want something as simple as possible (but no simpler). * The scrambling algorithm in the CVS client and server actually support more characters than those documented in *Note Password scrambling::. Someday we are going to either have to document them all (but this is not as easy as it may look, see below), or (gradually and with adequate process) phase out the support for other characters in the CVS implementation. This business of having the feature partly undocumented isn't a desirable state long-term. The problem with documenting other characters is that unless we know what character set is in use, there is no way to make a password portable from one system to another. For example, a with a circle on top might have different encodings in different character sets. It _almost_ works to say that the client picks an arbitrary, unknown character set (indeed, having the CVS client know what character set the user has in mind is a hard problem otherwise), and scrambles according to a certain octet<->octet mapping. There are two problems with this. One is that the protocol has no way to transmit character 10 decimal (linefeed), and the current server and clients have no way to handle 0 decimal (NUL). This may cause problems with certain multibyte character sets, in which octets 10 and 0 will appear in the middle of other characters. The other problem, which is more minor and possibly not worth worrying about, is that someone can type a password on one system and then go to another system which uses a different encoding for the same characters, and have their password not work. The restriction to the ISO646 invariant subset is the best approach for strings which are not particularly significant to users. Passwords are visible enough that this is somewhat doubtful as applied here. ISO646 does, however, have the virtue (!?) of offending everyone. It is easy to say "But the $ is right on people's keyboards! Surely we can't forbid that". From a human factors point of view, that makes quite a bit of sense. The contrary argument, of course, is that a with a circle on top, or some of the characters poorly handled by Unicode, are on _someone_'s keyboard.