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1 \documentclass{article}
2 \usepackage{makeidx}
3 \usepackage[margin=1.0in]{geometry}
5 \def\cvsrelease$Name: ${#1.#2}
6 \def\cvsdate$Date: 2002/07/11 17:45:50 ${#1-#2-#3}
8 \def\indexcommand#1
9 {\index{#1@{\tt #1} command}
10 \index{commands!#1@{\tt #1}}}
12 \def\indexglobalopt#1
13 {\index{#1@{\tt #1} option}
14 \index{global options!#1@{\tt #1}}}
16 \title{Version Control with Meta-CVS \cvsrelease$Name: $}
17 \date{\cvsdate$Date: 2002/07/11 17:45:50 $}
18 \author{Kaz Kylheku}
19 \makeindex
21 \begin{document}
22 \maketitle
23 \tableofcontents
25 \section{Introduction}
26 Greetings, reader! You are about to become a user of version control software
27 called Meta-CVS. This program uses another version control system called CVS
28 to store your documents, and also to store additional information about your
29 documents which allows it to provide useful behaviors that do not exist in CVS.
30 Effectively, Meta-CVS acts as an agent between you and CVS, which is easier
31 to use and more capable than CVS.
33 I wrote Meta-CVS because I was frustrated by the inability of CVS to treat the
34 directory structures of my projects as a versioned entity. At the same time, I
35 did not want to rewrite everything that already works well in CVS, such as
36 client-server operation, maintaining file version histories, and branching,
37 merging and conflict identification. Instead, I decided to write a software
38 layer which uses CVS as one of its building blocks. That software layer would
39 not only do completely new things, like directory structure versioning, but
40 also to automate certain tedious tasks which are normally performed with great
41 difficulty by the users of CVS.
43 Meta-CVS does not, and is not intended to, entirely shield you from knowing
44 anything about CVS. Firstly, Meta-CVS requires the CVS software and a CVS
45 repository. Users who want to use Meta-CVS have to know how to obtain and
46 install CVS and create a repository. Moreover, from time to time it is useful
47 or necessary to bypass Meta-CVS and invoke a CVS operation directly. This
48 guide does not teach CVS; you are strongly encouraged to read {\it Version
49 Management with CVS\/} by Per Cederqvist et al. \index{Cederqvist}
51 If you do not have a CVS repository to experiment with, please read enough of
52 the Cederqvist manual to find out how to create one. Set your {\tt CVSROOT}
53 environment variable to point to your repository and you are ready to
54 explore Meta-CVS.
55 \index{CVSROOT@{\tt CVSROOT}}
57 In this guide, a few typographic conventions are used. Text which
58 is stored into or produced by the computer is written in {\tt typewriter}
59 font. The first mention of any special terms is {\it italicized}. Such terms
60 are, for your convenience, gathered into a glossary in the appendix.
62 \section{Tutorial}
64 In this section, you will learn how to place a directory tree of files under
65 version control, check out that tree to create a working copy (also called a
66 {\it sandbox}), make changes in the sandbox and store the changes in the
67 repository. A directory of files independently versioned under Meta-CVS
68 is called a {\it module}, because it is represented as a CVS
69 module.\footnote{But note that unlike CVS, Meta-CVS does not support
70 the model of combining modules.}
71 \index{sandbox}
72 \index{module}
73 \index{mcvs program@{\tt mcvs} program}
74 \index{working copy|see {sandbox}}
76 Meta-CVS has a command line interface which is deliberately similar to that of
77 CVS. The program's name is {\tt mcvs}. The {\tt mcvs} program takes a
78 variety of arguments. The first argument is usually a word which specifies
79 a command. Oft used commands have two-letter abbreviations. For example the
80 {\tt update} command, whose abbreviation is {\tt up},
81 causes material in the repository to be integrated into the working copy.
83 Before the first argument, one may type special options. These are called
84 global options, and they influence the behavior of many commands in a similar
85 way. For example, when communicating with a remote repository over a slow
86 network, the {\tt -z} option may be used to specify a compression level.
87 \indexglobalopt{-z}
89 \subsection{Creating a Module}
90 \indexcommand{create}
92 The only way to create a module is to start with an existing directory
93 containing files and subdirectories, and invoke the {\tt create} command.
94 Suppose that your project is a compiler for a scripting language called Blorg,
95 and you want your module to be called {\tt blorg}. First, change to
96 the directory containing your latest Blorg sources:
97 \index{Blorg}
98 \begin{verbatim}
99 cd blorg-devel
100 \end{verbatim}
101 Then, invoke the command:
102 \begin{verbatim}
103 mcvs create blorg blorg-initial-version
104 \end{verbatim}
105 The {\tt create} command requires two additional arguments: the name of
106 the module, and a symbolic name which will identify the baseline of
107 newly versioned files. This name is known as a {\it tag}: more specificaly, a
108 {\it version tag}. Here, we have chosen the tag {\tt blorg-initial-version}.
109 Tags are very useful when one makes a module from a specific version of an
110 existing program. Suppose that you didn't write Blorg yourself; rather, you
111 have a copy of the Blorg 2.3 sources and would like to begin your own
112 independent stream of development. It would then behoove you, when creating the
113 module, to use a tag like {\tt blorg-2-3}. This tag could prove to be very
114 important later on; for example, when you want to create a branch from the 2.3
115 baseline, which will accept a new snapshot from the Blorg developers.
116 \index{tag}
117 \index{baseline}
119 The first action that the {\tt create} command takes is to scan the current
120 working directory, and, recursively, all of its subdirectories. It forms
121 a list of all regular files, ignoring any device special files, symbolic links
122 and the like. Having thus gathered a list of the files, it identifies all
123 of their {\it suffixes} and collates them to form a list.
125 If none of the files have suffixes, the creation procedure skips to the next
126 step. Otherwise, a text editor is invoked in order to allow you to make
127 alterations to a specification which tells how files having these various
128 suffixes are to be treated when they are stored into and retrieved from CVS.
129 The specification is written in the {\it Lisp\/} language, and may look
130 something like this:
131 \index{Lisp}
132 \begin{verbatim}
133 (("c" :DEFAULT)
134 ("lisp" :DEFAULT)
135 ("png" :DEFAULT)
136 ("txt" :DEFAULT))
137 \end{verbatim}
138 This is the notation for a list of four elements, as indicated by the
139 outermost parentheses which enclose the whole thing. Each of the four
140 elements is itself a list containing a string like {\tt "c"} and the
141 symbol {\tt :DEFAULT}. The string represents a file suffix, and the
142 symbol indicates how files having that suffix are to be treated.
143 In the text editor, you should see instructions which explain the
144 various keywords which are supported. The greatest concern is to
145 identify what files are binary. For example, in the above definition,
146 the treatment of the suffix {\tt .png} should be modified to {\tt :BINARY}
147 \index{binary@{\tt :binary}}
148 \index{default@{\tt :default}}
149 because most likely this suffix indicates a computer graphics image
150 in the Portable Network Graphics format, which is a binary format
151 that must not be subject to line ending conversions, nor to keyword expansion.
152 When you are done editing, save and quit; Meta-CVS will then proceed.
153 If you create a syntax error, for example by introducing an unbalanced
154 parenthesis, Meta-CVS will prompt you with an error message, and you will
155 be given an opportunity to correct the error in a new text editing session.
156 \index{png files@{\tt png} files}
158 Note that the symbols may be typed in any mixture of upper and lower
159 case---{\tt :Binary}, {\tt :binary}, {\tt :BiNaRy}, and so forth. These
160 all mean the same thing. However, the leading colon is required.\footnote{In
161 case you are interested, that colon is a special Lisp notation which indicates
162 that the following name refers to a symbol in the {\tt KEYWORD} package.}
164 Finally, Meta-CVS invokes CVS to create a new module in the repository.
165 CVS again, brings up a text editor. This time you are expected to enter
166 a log message which will be added to version 1.1 of every new document.
167 You are, in fact, interacting with {\tt cvs import}.
168 \index{CVS!import command@{\tt import} command}
170 \subsection{Checking out a Module}
172 Like CVS, and some other version control systems, Meta-CVS is based on sandbox
173 model. Under this model, documents are copied from a central repository, and users
174 work with copies of documents. Obtaining a copy is called checking out.
175 The Meta-CVS command for checking out is {\tt checkout}, abbreviated {\tt co}.
176 \indexcommand{checkout}
177 It takes one argument. Continuing with our Blorg example:
178 \begin{verbatim}
179 mcvs co blorg
180 \end{verbatim}
181 After a log of messages scrolls by in the terminal window, there should
182 now exist the subdirectory {\tt blorg}, and in that subdirectory there
183 should appear the project's source files. This is a working copy, or a sandbox.
184 You can check out more than one sandbox; sometimes that is convenient to do
185 when one needs to work on several completely unrelated tasks in the same
186 project. The CVS repository doesn't know anything about your sandbox; rather,
187 each sandbox contains information which points back to the repository from
188 which it was checked out. It is safe to move the sandbox by applying the {\tt
189 mv} command to its root directory.
190 \index{moving!a sandbox}
192 \subsection{Anatomy of a Sandbox}
194 In the root directory of the sandbox, as you will probably notice, there is a
195 subdirectory called {\tt MCVS}. This is where Meta-CVS stores its local
196 administrative files as well as versioned metadata. It is also where your
197 documents are checked out from CVS; effectively, this directory doubles as a
198 CVS sandbox.
199 \index{MCVS subdirectory@{\tt MCVS} subdirectory}
201 All your files have been assigned machine-generated names by Meta-CVS.
202 These names begin with the characters {\tt F-} followed by thirty-two
203 hexadecimal digits and an optional suffix. In Meta-CVS jargon, they are called
204 {\it F-files}. These files are connected to the directory structure of
205 the sandbox through {\it hard links}.
206 \index{hard link}
207 That is to say, each of the F-files
208 which appear under the {\tt MCVS} directory also exist in some other
209 directory within your sandbox. This arrangement is possible because your
210 operating system allows a file object to be referenced by more than one
211 directory entry. Directories are nothing more than lists which link names to
212 file objects. The same file can be known as {\tt
213 MCVS/F-0AA69D7C8A0A864345D90F45C18B8B58} as well as {\tt source/lib/hash.c}. In
214 order to delete the file from your filesystem, you have to delete both
215 directory entries.\footnote{This is why the POSIX system function for doing
216 this is called {\tt unlink}. Deleting a directory entry doesn't necessarily
217 mean that a file is gone, only that a link, possibly not the last remaining
218 link, has been erased. \index {unlink system function@{\tt unlink}
219 system function}}
220 \index{F-file}
222 When you check out a module, Meta-CVS calls upon CVS to retrieve
223 copies of F-files from the repository. Then it re-creates the directory
224 structure of the sandbox, inserting these files in the appropriate places
225 in that structure under their familiar names. This insertion is not done
226 by copying the F-files, but rather by creating links to them, which
227 is very efficient.
229 How does Meta-CVS remember the familar names of the F-files so that it can
230 construct the sandbox? This association is recorded in a file called {\tt MAP}
231 under the {\tt MCVS} directory, represented in Lisp notation. You are going
232 to have to understand the {\tt MAP} file sooner or later, because at times it
233 is necessary to manually edit that file. For example, it can happen that
234 several programmers independently change the mapping in a way that creates a
235 conflict. Resolving the conflict means loading the file into a text editor, and
236 manually sorting out the problem.
237 \index{MAP file@{\tt MAP} file}
239 Why does Meta-CVS assigns its own internal names to files, and stores
240 the user-assigned names in a special versioned document? The reason
241 is to make it possible to perform directory structure versioning,
242 which means that the directory structure of a module is versioned just
243 like the contents of its files. Changing the name or location of
244 a file is effectively just another edit that is commited to the repository.
246 \subsection{Making Changes}
248 Now that you have a working copy checked out, you are probably eager
249 to make some changes. This is quite easy; simply edit any of the
250 files to your satisfaction. The version control system knows that you
251 have edited the files; when you are ready, you can instruct
252 the software to publish your changes to the repository. Publishing
253 changes is known as {\it committing\/} and is performed using the {\tt commit}
254 command, abbreviated {\tt ci}:\footnote{This stands for check in,
255 which means the same thing as commit in the jargon of the RCS version control
256 system. RCS has a {\tt ci} command, and this abbreviation survived into
257 CVS.\index{RCS}}
258 \indexcommand{commit}
259 \begin{verbatim}
260 mcvs ci
261 \end{verbatim}
262 A text editor starts up, and you are expected to enter a commit comment.
263 You are interacting with CVS at this point; the procedure is exactly the
264 same as for CVS commits. However, there is one notable difference. The file names
265 you see listed in the usual comment lines which begin with {\tt CVS:} and which
266 will be removed are the F-file names, rather than the human-readable
267 names. Alas, CVS doesn't know about the mapping, and this text
268 is prepared within the innards of CVS! Meta-CVS has a solution, though not an entirely
269 satisfactory one, in the form of a text filtering command which
270 reads arbitrary text on standard input, and copies it to standard output,
271 filtering F-file names to their human-readable counterparts. This command
272 is {\tt filt}, abbreviated~{\tt fi}.
273 \indexcommand{filt}
274 Decent text editors allow portions of the text to be easily filtered through
275 an external command. For example, in the vi editor, the command
276 {\tt :\%!mcvs fi} command will apply the Meta-CVS filter to the entire edit
277 buffer. It's trivial to bind this this command to a control character, and
278 store this definition in the editor's personal configuration file, so that the
279 action can be repeated by typing one or two keystrokes.
281 \subsection{Adding Files}
283 Some kinds of changes require special steps to inform Meta-CVS of
284 your intent. For example, if you decide to add some files, Meta-CVS
285 will not automatically incorporate them into the module. For obvious
286 reasons, a sandbox is allowed to contain a mixture of local files and
287 versioned files; there is no certain way to tell which local files ought
288 to be versioned. An object file which results from compiling source
289 code almost certainly does not belong under version control, whereas a
290 new source file probably does. Or does it? It may be a temporary module
291 introduced for debugging, or some experimental code. Only the programmer
292 knows whether it ought to be published to the repository. Every file that
293 is added under version control initially starts out as a local file. An
294 explicit {\tt add} command must be invoked to cause a local file to become
295 versioned. This is a local change until it is committed to the repository,
296 at which point the newly added file becomes visible to other sandboxes.
298 \indexcommand{add}
299 Adding files is accomplished using the {\tt add} command. The add command
300 requires additional arguments which specify what files are to be added.
301 For exaple, to add the local files {\tt macros.lisp} and {\tt README},
302 issue the command:
303 \begin{verbatim}
304 mcvs add macros.lisp README
305 \end{verbatim}
306 Unlike CVS, Meta-CVS allows you to add entire subdirectories at a time.
307 The arguments can be any mixture of files and subdirectories; however,
308 subdirectories are only added if the {\tt -R} option is specified.
309 For example, to add the directories {\tt sources}, {\tt documentation}
310 and the file {\tt INSTALL}.
311 \begin{verbatim}
312 mcvs add -R sources documentation INSTALL
313 \end{verbatim}
314 \index{-R option@{\tt -R} option!of add@of {\tt add}}
315 Like the {\tt create} command, the {\tt add} command scans the
316 files to be added, and computes a list of their suffixes. If there
317 are any hitherto unknown suffixes in the added set, a text editor
318 will be invoked to allow you to specify the treatment of these
319 files.
320 The effect of {\tt mcvs add} is local; the files aren't incorporated
321 into the repository until a commit takes place.
323 \subsection{Reviewing Changes}
325 Before committing local changes, one usually wants to review what those changes
326 are; to find out what files have been added, removed, moved or modified, and to
327 view the differences in modified files.
330 \appendix
332 \section{Glossary}
334 \paragraph{baseline} A crosscut through a collection of version-controlled
335 documents, which selects a specific version of each document.
336 \index{baseline}
338 \paragraph{basename} The short name of a file, excluding the fullp path,
339 if any. For example, the basename of {\tt src/lib/lexer.c} is {\tt lexer.c}.
340 \index{basename}
342 \paragraph{commit} To publish local changes to the repository, thereby
343 permanently integrating them into the project history. Commited changes
344 can be picked up in other sandboxes by {\it update}.
346 \paragraph{CVS} Concurrent Versions System. A popular freeware version control
347 suite widely used by free software projects. CVS started as a set of shell
348 scripts written by Dick Grune, who posted the software to Usenet in 1986.
349 Grune's CVS scripts used RCS; they provided higher-level functionality over
350 RCS, automating and simplifying the use of RCS by for instance applying version
351 control operations such as merging to entire sets of files at once.
352 Eventually, CVS was rewritten in C, and directly incorporated the algorithms
353 from RCS while remaining compatible with the RCS file format.
354 \index{CVS}
356 \paragraph{F-file} A user document stored by Meta-CVS, in CVS, having a
357 machine-generated name consisting of the characters {\tt F-} followed
358 by thirty-two hexadecimal digits and an optional suffix.
359 \index{F-file}
361 \paragraph{hard link} An association connecting a directory entry to a file
362 object.
363 \index{hard link}
365 \paragraph{Lisp} {\bf 1.} The standard computing language {\it ANSI Common
366 Lisp}. {\bf 2.} Printed notation, conforming to the ANSI Common Lisp syntax,
367 expressing a potentially complex, nested data structure. {\bf 3.} Program code
368 resulting from the reinterpretation of Lisp data structures as programming
369 language constructs.
370 \index{Lisp}
372 \paragraph{module} An independent set of documents managed as a unit using
373 Meta-CVS.
374 \index{module}
376 \paragraph{sandbox} The working copy of your project.
377 \index{sandbox}
379 \paragraph{suffix} The trailing portion of a {\it basename} which is separated
380 from the rest of the name by a period (.) character. If there are two or
381 more such characters, then it is the longest such portion. If the basename
382 contains no periods, then it has no suffix. If the basename begins with a
383 period, the rest of that entire name is a suffix. Examples:
384 the suffix of {\tt lint.tar.gz} is {\tt tar.gz}; that of {\tt .xshell.rc}
385 is {\tt xshell.rc}; the suffix of {\tt foo.} is the empty string; and neither
386 {\tt .clisprc} nor {\tt README} have a suffix.
387 \index{suffix}
389 \paragraph{tag} A symbolic revision which identifies a {\it baseline}. Tags
390 are used by disciplined developers, or configuration managers, to label
391 software releases so that it is possible to later retrieve the exact baseline
392 of any given release.
393 \index{tag}
395 \paragraph{update} In CVS parlance, to retrieve a version of one or more
396 documents from the repository, merge it with local changes made to the sandbox
397 copy, if any, and then replace that copy. Updating is not only used to
398 incorporate the latest changes from the repository into a sandbox, while
399 preserving any outstanding local modifications, but it is also used for
400 ``navigating'' to old versions and switching among branches.
402 \index{renaming|see {moving}}
403 \printindex
404 \end{document}

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