1 Important notes on Mercurial repository access for Isabelle
2 ===========================================================
7 1a. Linux and Mac OS X: ensure that Perl (with libwww) and Mercurial (hg)
8 is installed (see also http://www.selenic.com/mercurial)
10 1b. Windows: ensure that Cygwin with Mercurial and Perl is installed (see
11 also http://www.cygwin.com)
13 2. Clone repository (bash shell commands):
15 hg clone http://isabelle.in.tum.de/repos/isabelle
19 ./bin/isabelle components -I
21 ./bin/isabelle components -a
23 ./bin/isabelle jedit -l HOL
25 ./bin/isabelle build -b HOL #optional: build session image manually
27 3. Update repository (bash shell commands):
33 ./bin/isabelle components -a
35 ./bin/isabelle jedit -l HOL
37 ./bin/isabelle jedit -b -f #optional: force fresh build of Isabelle/Scala
39 4. Access documentation (bash shell commands):
41 ./bin/isabelle build_doc -a
43 ./bin/isabelle doc system
49 Mercurial http://www.selenic.com/mercurial belongs to the current
50 generation of source code management systems that follow the so-called
51 paradigm of "distributed version control". This is a terrific name
52 for plain revision control without the legacy of CVS or SVN. See also
53 http://hginit.com/ for an introduction to the main ideas. The
54 Mercurial book http://hgbook.red-bean.com/ explains many more details.
56 Mercurial offers great flexibility in organizing the flow of changes,
57 both between individual developers and designated pull/push areas that
58 are shared with others. This additional power demands some additional
59 responsibility to maintain a certain development process that fits to
62 Regular Mercurial operations are strictly monotonic, where changeset
63 transactions are only added, but never deleted or mutated. There are
64 special tools to manipulate repositories via non-monotonic actions
65 (such as "rollback" or "strip"), but recovering from gross mistakes
66 that have escaped into the public can be hard and embarrassing. It is
67 much easier to inspect and amend changesets routinely before pushing.
69 The effect of the critical "pull" / "push" operations can be tested in
70 a dry run via "incoming" / "outgoing". The "fetch" extension includes
71 useful sanity checks beyond raw "pull" / "update" / "merge", although
72 it has lost popularity in recent years. Most other operations are
73 local to the user's repository clone. This gives some freedom for
74 experimentation without affecting anybody else.
76 Mercurial provides nice web presentation of incoming changes with a
77 digest of log entries; this also includes RSS/Atom news feeds. There
78 are add-on history browsers such as "hg view" and TortoiseHg. Unlike
79 the default web view, some of these tools help to inspect the semantic
80 content of non-trivial merge nodes.
86 The main Isabelle repository can be cloned like this:
88 hg clone http://isabelle.in.tum.de/repos/isabelle
90 This will create a local directory "isabelle", unless an alternative
91 name is specified. The full repository meta-data and history of
92 changes is in isabelle/.hg; local configuration for this clone can be
93 added to isabelle/.hg/hgrc, but note that hgrc files are never copied
94 by another clone operation.
97 There is also $HOME/.hgrc for per-user Mercurial configuration. The
98 initial configuration requires at least an entry to identify yourself
104 Isabelle contributors are free to choose either a short "login name"
105 (for accounts at TU Munich) or a "full name" -- with or without mail
106 address. It is important to stick to this choice once and for all.
107 The machine default that Mercurial produces for unspecified
108 [ui]username is not appropriate.
110 Such configuration can be given in $HOME/.hgrc (for each home
111 directory on each machine) or in .hg/hgrc (for each repository clone).
114 Here are some further examples for hgrc. This is how to provide
115 default options for common commands:
120 This is how to configure some extension, which is called "graphlog"
121 and provides the "glog" command:
127 Shared pull/push access
128 -----------------------
130 The entry point http://isabelle.in.tum.de/repos/isabelle is world
131 readable, both via plain web browsing and the hg client as described
132 above. Anybody can produce a clone, change it locally, and then use
133 regular mechanisms of Mercurial to report changes upstream, say via
134 mail to someone with write access to that file space. It is also
135 quite easy to publish changed clones again on the web, using the
136 ad-hoc command "hg serve -v", or the hgweb.cgi or hgwebdir.cgi scripts
137 that are included in the Mercurial distribution, and send a "pull
138 request" to someone else. There are also public hosting services for
139 Mercurial repositories, notably Bitbucket.
141 The downstream/upstream mode of operation is quite common in the
142 distributed version control community, and works well for occasional
143 changes produced by anybody out there. Of course, upstream
144 maintainers need to review and moderate changes being proposed, before
145 pushing anything onto the official Isabelle repository at TUM. Direct
146 pushes are also reviewed routinely in a post-hoc fashion; everybody
147 hooked on the main repository is called to keep an eye on incoming
148 changes. In any case, changesets need to be understandable, both at
149 the time of writing and many years later.
151 Push access to the Isabelle repository requires an account at TUM,
152 with properly configured ssh to isabelle-server.in.tum.de. You also
153 need to be a member of the "isabelle" Unix group.
155 Sharing a locally modified clone then works as follows, using your
156 user name instead of "wenzelm":
158 hg out ssh://wenzelm@isabelle-server.in.tum.de//home/isabelle-repository/repos/isabelle
160 In fact, the "out" or "outgoing" command performs only a dry run: it
161 displays the changesets that would get published. An actual "push",
162 with a lasting effect on the Isabelle repository, works like this:
164 hg push ssh://wenzelm@isabelle-server.in.tum.de//home/isabelle-repository/repos/isabelle
167 Default paths for push and pull can be configured in
168 isabelle/.hg/hgrc, for example:
171 default = ssh://wenzelm@isabelle-server.in.tum.de//home/isabelle-repository/repos/isabelle
173 Now "hg pull" or "hg push" will use that shared file space, unless a
174 different URL is specified explicitly.
176 When cloning a repository, the default path is set to the initial
177 source URL. So we could have cloned via that ssh URL in the first
178 place, to get exactly to the same point:
180 hg clone ssh://wenzelm@isabelle-server.in.tum.de//home/isabelle-repository/repos/isabelle
186 The main idea of Mercurial is to let individual users produce
187 independent branches of development first, but merge with others
188 frequently. The basic hg merge operation is more general than
189 required for the mode of operation with a shared pull/push area. The
190 "fetch" extension accommodates this case nicely, automating trivial
191 merges and requiring manual intervention for actual conflicts only.
193 The fetch extension can be configured via $HOME/.hgrc like this:
201 To keep merges semantically trivial and prevent genuine merge
202 conflicts or lost updates, it is essential to observe to following
203 general discipline wrt. the public Isabelle push area:
205 * Before editing, pull or fetch the latest version.
207 * Accumulate private commits for a maximum of 1-3 days.
209 * Start publishing again by pull or fetch, which normally produces
212 * Test the merged result, e.g. like this:
216 * Push back in real time.
218 Piling private changes and public merges longer than 0.5-2 hours is
219 apt to produce some mess when pushing eventually!
221 The pull-test-push cycle should not be repeated too fast, to avoid
222 delaying others from doing the same concurrently.
228 The following principles should be kept in mind when producing
229 changesets that are meant to be published at some point.
231 * The author of changes needs to be properly identified, using
232 [ui]username configuration as described above.
234 While Mercurial also provides means for signed changesets, we want
235 to keep things simple and trust that users specify their identity
236 correctly (and uniquely).
238 * The history of sources is an integral part of the sources
239 themselves. This means that private experiments and branches
240 should not be published by accident. Named branches are not
241 allowed on the public version. Note that old SVN-style branching
242 is replaced by regular repository clones in Mercurial.
244 Exchanging local experiments with some other users can be done
245 directly on peer-to-peer basis, without affecting the central
248 * Log messages are an integral part of the history of sources.
249 Other people will have to inspect them routinely, to understand
250 why things have been done in a certain way at some point.
252 Authors of log entries should be aware that published changes are
253 actually read. The main point is not to announce novelties, but
254 to describe faithfully what has been done, and provide some clues
255 about the motivation behind it. The main recipient is someone who
256 needs to understand the change in the distant future to isolate
257 problems. Sometimes it is helpful to reference past changes
258 formally via changeset ids in the log entry.
260 * The standard changelog entry format of the Isabelle repository
261 admits several (somehow related) items to be rolled into one
262 changeset. Each item is then described on a separate line that
263 may become longer as screen line and is terminated by punctuation.
264 These lines are roughly ordered by importance.
266 This format conforms to established Isabelle tradition. In
267 contrast, the default of Mercurial prefers a single headline
268 followed by a long body text. The reason for that is a somewhat
269 different development model of typical "distributed" projects,
270 where external changes pass through a hierarchy of reviewers and
271 maintainers, until they end up in some authoritative repository.
272 Isabelle changesets can be more spontaneous, growing from the
275 The web style of http://isabelle.in.tum.de/repos/isabelle/
276 accommodates the Isabelle changelog format. Note that multiple
277 lines will sometimes display as a single paragraph in HTML, so
278 some terminating punctuation is required. Do not squeeze multiple
279 items on the same line in the original text!
282 Testing of changes (before push)
283 --------------------------------
285 The integrity of the standard pull/push area of Isabelle needs the be
286 preserved at all time. This means that a complete test with default
287 configuration needs to be finished successfully before push. If the
288 preparation of the push involves a pull/merge phase, its result needs
289 to covered by the test as well.
291 There are several possibilities to perform the test, e.g. using the
292 Isabelle testboard at TUM. In contrast, the subsequent command-line
293 examples are for tests on the local machine:
295 ./bin/isabelle build -a #regular test
297 ./bin/isabelle build -a -o document=pdf #test with document preparation
299 ./bin/isabelle build -a -j2 -o threads=4 #test on multiple cores (example)
301 See also the chapter on Isabelle sessions and build management in the
304 Note that implicit dependencies on Isabelle components are specified
305 via catalog files in $ISABELLE_HOME/Admin/components/ as part of the
306 Mercurial history. This allows to bisect over a range of Isabelle
307 versions while references to the contributing components change
308 accordingly. Recall that "isabelle components -a" updates the local
309 component store monotonically according to that information, and thus
310 resolves missing components.