--- a/man/xemacs-faq.texi	Wed Feb 10 13:46:54 2010 +0900
+++ b/man/xemacs-faq.texi	Wed Feb 10 20:51:51 2010 +0900
@@ -188,7 +188,8 @@
 * Advanced::              Advanced Customization Using XEmacs Lisp.
 * Other Packages::        Other External Packages.
 * Current Events::        What the Future Holds.
-* Legacy Versions::       New information about old XEmacsen.
+* Legacy Versions::       New Information about Old XEmacsen.
+* Bleeding Edge::         Working with XEmacs Source Code Repositories.
 
 @detailmenu
  --- The Detailed Node Listing ---
@@ -567,6 +568,27 @@
 * Q10.0.1::   Gnus 5.10 won't display smileys in XEmacs 21.1.
 * Q10.0.2::   XEmacs won't start on Windows in XEmacs 21.1.
 
+11 Working with XEmacs source code repositories
+
+11.0: The XEmacs repositories
+* Q11.0.1::   Where is the most recent XEmacs development code?
+* Q11.0.2::   Where is the most recent XEmacs stable code?
+* Q11.0.3::   Where is the most recent XEmacs package code?
+* Q11.0.4::   Why isn't @var{package} available? and what to do about it.
+* Q11.0.5::   How do I get commit access?
+
+11.1: Working with CVS
+* Q11.1.1::   How do I keep cool using CVS?
+
+11.2: Working with Mercurial
+* Q11.2.1::   What is Mercurial?
+* Q11.2.2::   Where do I get Mercurial?
+* Q11.2.3::   Do I really have to waste space on history?
+* Q11.2.4::   @code{hg diff} gives bizarre output.
+* Q11.2.5::   How do I recover from a bad commit?  (I already pushed.)
+* Q11.2.6::   How do I recover from a bad commit?  (I haven't pushed yet.)
+* Q11.2.7::   Testing patches with Mercurial Queues.
+
 @end detailmenu
 @end menu
 
@@ -8669,7 +8691,7 @@
 For older news, see the file @file{ONEWS} in the @file{etc} directory of
 the XEmacs distribution.
 
-@node Legacy Versions,  , Current Events, Top
+@node Legacy Versions,  Bleeding Edge, Current Events, Top
 @unnumbered 10 New information about old XEmacsen
 
 This is part 10 of the XEmacs Frequently Asked Questions list.  It will
@@ -8745,4 +8767,550 @@
 binaries, but you can use the 21.1 binaries if you are very paranoid
 about stability.  @xref{Q1.1.2, Are binaries available?}.
 
+
+@node Bleeding Edge, , Legacy Versions, Top
+@unnumbered 10 Working with XEmacs Source Code Repositories.
+
+This is part 11 of the XEmacs Frequently Asked Questions list.  The
+primary purpose is advice on use of the version control systems used to
+keep the history of XEmacs development.
+
+@menu
+11.0: The XEmacs repositories
+* Q11.0.1::   Where is the most recent XEmacs development code?
+* Q11.0.2::   Where is the most recent XEmacs stable code?
+* Q11.0.3::   Where is the most recent XEmacs package code?
+* Q11.0.4::   Why isn't @var{package} available? and what to do about it.
+* Q11.0.5::   How do I get commit access?
+
+11.1: Working with CVS
+* Q11.1.1::   How do I keep cool using CVS?
+
+11.2: Working with Mercurial
+* Q11.2.1::   What is Mercurial?
+* Q11.2.2::   Where do I get Mercurial?
+* Q11.2.3::   Do I really have to waste space on history?
+* Q11.2.4::   @code{hg diff} gives bizarre output.
+* Q11.2.5::   How do I recover from a bad commit?  (I already pushed.)
+* Q11.2.6::   How do I recover from a bad commit?  (I haven't pushed yet.)
+* Q11.2.7::   Testing patches with Mercurial Queues.
+@end menu
+
+
+@node Q11.0.1, Q11.0.2, Bleeding Edge, Bleeding Edge
+@unnumberedsubsec Where is the most recent XEmacs development code?
+
+The most recent XEmacs @emph{development} code is kept in a Mercurial
+repository, hosted by the Debian project.  The read-only URL, for
+anybody who doesn't intend to push upstream directly, is
+
+@example
+http://hg.debian.org/hg/xemacs/xemacs
+@end example
+
+The read-write URL for committers is
+
+@example
+ssh://sperber-guest@@hg.debian.org//hg/xemacs/xemacs
+@end example
+
+Yes, Virginia, that doubled slash is correct.
+
+@xref{Q11.0.5, How do I get commit access?}.
+
+@xref{Q11.2.1, What is Mercurial?}.
+
+@node Q11.0.2, Q11.0.3, Q11.0.1, Bleeding Edge
+@unnumberedsubsec Where is the most recent XEmacs stable code?
+
+The most recent XEmacs @emph{stable} code is kept in a Mercurial
+repository, hosted by the Debian project.  The read-only URL is
+
+@example
+http://hg.debian.org/hg/xemacs/xemacs-21.4
+@end example
+
+If you're @emph{not} Vin, you don't need commit access.  If you
+@emph{are} Vin, you shouldn't need to refer to this FAQ.
+
+@xref{Q11.2.1, What is Mercurial?}.
+
+
+@node Q11.0.3, Q11.0.4, Q11.0.2, Bleeding Edge
+@unnumberedsubsec Where is the most recent XEmacs package code?
+
+The most recent XEmacs @emph{packages} code is kept in a CVS
+repository, hosted by the Debian project.  The read-only @code{CVSROOT},
+for anybody who doesn't intend to push upstream directly, is
+
+@example
+CVSROOT=:pserver:anonymous@@cvs.alioth.debian.org:/cvsroot/xemacs
+@end example
+
+The read-write @code{CVSROOT} for committers is
+
+@example
+CVSROOT=:ext:@var{aliothuser}@@cvs.alioth.debian.org:/cvsroot/xemacs
+@end example
+
+where @var{aliothuser} is your account on @code{alioth.debian.org}.  Then
+
+@example
+cvs checkout packages
+@end example
+
+as usual.  For more information, see
+@uref{http://www.xemacs.org/Develop/cvsaccess.html, XEmacs CVS Archive}
+on the website.
+
+@xref{Q11.1.1, How do I stay cool using CVS?}.
+
+@xref{Q11.0.5, How do I get commit access?}.
+
+
+@node Q11.0.4, Q11.0.5, Q11.0.3, Bleeding Edge
+@unnumberedsubsec Why isn't @var{package} available? and what to do about it.
+
+If a package isn't available from the Packages repository, probably
+nobody has shown enough interest to add it yet.  (Occasionally, there is
+a better package already in the XEmacs repository, of course.)
+
+The first step is to ask about it, and propose addition, on
+@email{xemacs-beta@@xemacs.org, the XEmacs Contributors list}.
+
+Most regular XEmacs contributors already shoulder primary responsibility
+for several packages, and contribute to maintenance of the rest, so you
+are unlikely to get a massively enthusiastic response unless you
+volunteer to become the maintainer of the version packaged for XEmacs
+yourself.  The duties are not terribly onerous if you're an active user
+of the package @ref{(xemacs-devguide)XEmacs Package Maintainer}.
+
+
+@node Q11.0.5, Q11.1.1, Q11.0.4, Bleeding Edge
+@unnumberedsubsec How do I get commit access?
+
+To get commit access to XEmacs code, write to
+@email{xemacs-review@@xemacs.org, the XEmacs Review Board} and request
+it.  Once approved, for the development code, you also need to send
+@email{mike@@xemacs.org, Michael Sperber} your SSH v2 RSA key (Alioth
+policy; v1 and DSA keys aren't acceptable).  A CC to
+@email{xemacs-services@@xemacs.org, the XEmacs Services team} is a good
+idea, although not absolutely necessary.  You should also get an Alioth
+account so that you can publish branches for review.
+
+For packages code, you must get an Alioth account.  Send your account
+name information to @email{xemacs-services@@xemacs.org, the XEmacs
+Services team}.
+
+The stable repository is gated; only the gatekeeper (currently Vin
+Shelton) has commit access.  Patches for the stable repository should be
+submitted to @email{xemacs-patches@@xemacs.org, XEmacs Patches}, as usual.
+
+@uref{http://www.xemacs.org/Develop/hgaccess.html, XEmacs Mercurial Archive}
+
+@uref{http://www.xemacs.org/Develop/cvsaccess.html, XEmacs CVS Archive}
+
+@xref{Q11.1.1, How do I stay cool using CVS?}.
+
+@xref{Q11.2.1, What is Mercurial?}.
+
+
+@node Q11.1.1, Q11.2.1, Q11.0.5, Bleeding Edge
+@unnumberedsubsec How do I keep cool using CVS?
+
+You don't.  CVS is just basically and in detail @emph{un}-cool.
+
+What would be really cool is if you would help us out in moving the
+packages repository to Mercurial.  Volunteer on
+@email{xemacs-beta@@xemacs.org, the XEmacs Contributors list}.  What's
+needed is to figure out how to provide a one step checkout for the whole
+package hierarchy, while restricting commits to one package at a time.
+
+For help using CVS, Google or ask on @email{xemacs-beta@@xemacs.org}.
+Please update this FAQ with one or two of the best references you find.
+
+
+@node Q11.2.1, Q11.2.2, Q11.1.1, Bleeding Edge
+@unnumberedsubsec What is Mercurial?
+
+Mercurial is a @dfn{distributed version control system}, or DVCS.  This
+means that versioning information can be easily exchanged between
+different lines of development, even if located on different hosts.  In
+the older @dfn{centralize version control system} model, when you
+@dfn{commit} a change, it is immediately reflected in the public
+repository.  In a DVCS, each user has a @dfn{local repository}, and
+the commit operation creates a version in that repository.  To
+communicate with the public repository, a separate @dfn{push} operation
+must be executed.  The DVCS model is more appropriate for open source
+development.
+
+@itemize
+@item
+The VCS model mirrors the development organization, where developers
+tend to work independently or in very small groups.
+
+@item
+Users without commit access can conveniently manage their local changes.
+
+@item
+Developers can work, and commit changes, while disconnected from the
+Internet.  Then they merge and push their changes later.
+@end itemize
+
+Use of a DVCS does require some changes in workflow, but the XEmacs
+developers consider that inconvenience to be far more than balanced by
+the advantages.
+
+
+@node Q11.2.2, Q11.2.3, Q11.2.1, Bleeding Edge
+@unnumberedsubsec Where do I get Mercurial?
+
+Most OS distributions (including add-on distributions like
+@uref{http://www.cygwin.com/, Cygwin} and
+@uref{http://www.macports.org/, MacPorts}) include Mercurial packages.
+Of course, you can get the source distribution, as well as pre-built
+packages for most major platforms, from
+@uref{http://mercurial.selenic.com/wiki/, the Mercurial developers}.
+
+
+@node Q11.2.3, Q11.2.4, Q11.2.2, Bleeding Edge
+@unnumberedsubsec Do I really have to waste space on history?
+
+Yes, you do.  It's really not that much, though.  In one of my current
+workspaces, I see
+
+@table @code
+@item XEmacs source files (and other cruft, such as editor backups)
+115464KB
+@item Build products
+49676
+@item Mercurial control files and history
+25644
+@end table
+
+That really does include all of the history available in the main XEmacs
+development branch, and the build products are near twice the size of
+all of the Mercurial-specific information.
+
+
+@node Q11.2.4, Q11.2.5, Q11.2.3, Bleeding Edge
+@unnumberedsubsec @code{hg diff} gives bizarre output.
+
+You may see an unreasonable diff (often large) that doesn't seem to
+reflect your work.
+
+This is usually due to using @code{hg diff} on a @dfn{merge commit}.
+That means the commit has multiple parents, and joins together two lines
+of development that occured concurrently.
+
+You're diffing against the "wrong" one; try the other one.  You get the
+relevent revision number or ID from @code{hg log}.  In more detail:
+
+When there is a merge in Mercurial, it will often be the case that
+one of the parents is the immediate predecessor of the merge
+commit.  @code{hg log} will report something like
+
+@example
+    changeset:   4789:56049bea9231    # revision D, below
+    parent:      4788:5cca06f930ea    # your commit
+    parent:      4787:6e6f7b79c1fc    # diff against this
+    user:        you (or somebody else)
+
+    changeset:   4788:5cca06f930ea    # revision B, below
+    parent:      4760:217abcf015c4    # revision A, below
+    user:        you
+
+    changeset:   4787:6e6f7b79c1fc    # revision C, below
+    parent:      4786:d6cfba1cc388
+    user:        somebody else
+@end example
+
+Note that the divergence took place a long time ago (r4760).
+It's natural to diff against (tip - 1), in the example above,
+@code{hg diff -r 4788}.  But this will give unexpected output!
+
+A picture of this history looks something like
+
+@example
+      B --- D
+     /     /
+    A ... C
+@end example
+
+where A is the common ancestor, B is the commit you did, C is the
+mainline at the time of the merge, and D is the merge commit.  The
+three dots between A and C can represent many commits, and a lot
+of work.  Given no conflicts in the merge, @code{hg diff -r C -r D} is
+the same as @code{hg diff -r A -r B}, @emph{i.e.}, it shows your work.
+Similarly, @code{hg diff -r B -r D} is the same as
+@code{hg diff -r A -r C}.  This latter diff is likely to be quite large,
+and it doesn't show your work.  Unfortunately, that is the typical
+result of diffing against the "previous" commit.
+
+@node Q11.2.5, Q11.2.6, Q11.2.4, Bleeding Edge
+@unnumberedsubsec How do I recover from a bad commit?  (I already pushed.)
+
+Once upon a time, an XEmacs developer wrote:
+
+ > GAAAAK!  What's the best way to restore ChangeLog and its history?
+
+He had just inadvertantly pushed a commit which deleted
+@file{src/ChangeLog}!  The history is still there, not to worry.  (In
+this case, another developer had restored src/ChangeLog already.)  The
+best way depends on a number of things.  First, let's look at the log
+and the state of the DAG (the graph of commits).  Here's the log,
+formatted somewhat differently from the usual output for compactness.
+
+@example
+5025    anne    Restore src/ChangeLog.
+5024    barb    merge
+        parents: 5023 5010
+5023    barb    Error-checking.
+5020    barb    merge
+        parents: 5019 5006 
+5019    barb    Fix non-Mule build.
+5011    barb    Some internals-manual updates.
+        parents: 5002
+5010    cary    Windows fixes for Visual Studio 6.
+        parents: 5008 5009
+5009    cary    Miscellaneous small fixes to Windows VS6 build.
+        parents: 5006
+5008    dana    Add license information.
+5007    dana    Relicense emodules.texi.
+5006    cary    Instantiate compile fix for nt.c.
+5005    edna    Cast correctly.
+5003    edna    #'union doesn't preserve relative order
+5002    barb    Fix some compile bugs.
+@end example
+
+(The gaps at 5003...5005, 5011...5019, and 5020...5023 are filled with
+sequences of commits by the same developers.)  Let's visualize this as a
+graph.  Time increases to the right, the leading "50" is omitted for
+brevity, and the dotted links indicate that several irrelevant commits
+were omitted, also for brevity.
+
+@example
+                        ,------ 09 -----.
+                       /                 \
+02 --- 03 ... 05 --- 06 --- 07 --- 08 --- 10 --- 24 --- 25
+  \                    \                        /
+   `-- 11 ... 19 -------`-- 20 ... 23 ---------'
+@end example
+
+The "problem commit" is 5010, which merges 5008 with 5009, and somehow
+managed to "lose" @file{src/ChangeLog}.  The unobvious consequence is
+that, although the @emph{other} changes made in 5007 and 5008 were
+successfully merged and are present in 5010, the log entry made by
+Dana for 5008 "just disappeared".  (The log entry for 5007 is in a
+different @file{ChangeLog}, so it's safe.)
+
+@subsubheading The safe and simple way for Cary
+
+To recover state file-by-file (also for whole directories), use @code{hg
+revert}.  This does not change the "current" version, @emph{i.e.}, the
+commit that will be the parent for your next commit.
+
+If it's not a merge commit, it's simple to restore the ChangeLog.  It's
+best to do it before making any other commits in your own workspace, and
+before pulling in new commits from others.  If there are a lot of such
+commits in your workspace already, ask for help.  But in this case,
+there was no such problem.  Just
+
+@example
+hg revert -r 5009 src/ChangeLog
+# Add Dana's log entry by hand.
+hg commit -m "Restore src/ChangeLog."
+@end example
+
+5009 is the revision id of the most recent commit that had the correct
+version of the file.  You get that from the "parent" field in @code{hg
+log}, or from the DAG browser (@code{hg view}, requires @code{hgk}
+extension enabled).
+
+Alternatively, Cary could revert from 5008.  This would leave her with
+@emph{her} log entry for 5009 missing, and that would have to be added
+by hand.
+
+Note that in the actual history, Cary didn't realize that Dana's log
+went missing, so Anne had to pick up the slack in 5025.
+
+@subsubheading Recovery by another developer
+
+Another way to recover earlier state is with @code{hg checkout} (or
+@code{hg update}, which is another way to spell the same command).  This
+changes the version that hg sees as "current", as well as reverting the
+workspace.
+
+A common scenario is that another developer, such as Barb in the log
+above, was already working on @file{src/ChangeLog}, saves her copy, then
+tries to merge.  She would then get a modify/delete conflict.  It's
+tempting to just resolve that in favor of keeping the file, and commit.
+This often works, but an alternative way uses the VCS:
+
+@example
+hg checkout 5010
+hg revert -r 5009 src/ChangeLog
+# Add Dana's log entry by hand.
+hg commit -m "Restore src/ChangeLog."
+@end example
+
+to get the same effect as described above, then
+
+@example
+hg merge
+@end example
+
+(making her changes "float to the top" of the log) or
+
+@example
+hg checkout 5023
+hg merge
+@end example
+
+(putting the Cary's branch at the top of the log).  This assumes she has
+no other heads in her workspace.  If she does have other heads she would
+have to use an explicit argument to @code{hg merge}.
+
+Note that in the actual history, Barb didn't realize that Dana's log
+went missing, so Anne (or somebody) had to pick up the slack in 5025.
+
+@subsubheading The hard but accurate way
+
+Suppose Barb did @code{hg pull -u}, but notices the problem before
+resolving conflicts and committing the merge.  Assume Barb was fully committed
+before doing @code{hg pull -u}.
+
+@example
+# Restore the ChangeLog, "covering up" the broken commit.
+# Check out Cary's head.  This nukes the merged files in the workspace,
+# but @emph{the history and versions in Barb's rev. 5023 are preserved
+# in the repository}.  The -C is necessary to overwrite files.
+hg checkout -C 5010
+hg revert -r 5009 src/ChangeLog
+# Merge Dana's branch (yes, again).
+# The repeated merge outside of src/ChangeLog should resolve to a
+# no-op, but the ChangeLog probably conflicts.
+# The -f is needed because revert leaves uncommitted changes.
+hg merge -f 5008
+hg commit -m "Re-merge Dana's branch to recover her logs."
+# Merge Barb's work.
+# If Barb has only two heads, which seems likely, the argument to
+# merge is optional.
+hg merge 5023
+hg commit -m merge
+@end example
+
+Visualizing this with a graph, we have:
+
+@example
+                        ,------ 09 -----.
+                       /                 \
+02 --- 03 ... 05 --- 06 --- 07 --- 08 --- 10 *** 24 --- 25
+  \                    \             \          /      /
+   \                    \             `--------'      /
+    \                    \                           /
+     `-- 11 ... 19 -------`-- 20 ... 23 ------------'
+@end example
+
+Note that the versions 5024 and 5025 in this graph denote
+@emph{different} versions from the actual history.  The starred link
+means that editing work (aside from resolving conflicts) was done, on
+top of the merge.  However, the editing work is actually done by
+Mercurial (the revert command)!
+
+
+@node Q11.2.6, Q11.2.7, Q11.2.5, Bleeding Edge
+@unnumberedsubsec How do I recover from a bad commit?  (I haven't pushed yet.)
+
+If you hadn't yet pushed the commit you now regret, and realize it
+before doing further commits, you can use @code{hg strip tip}.  Then
+just redo the commit, possibly with additional changes before
+committing.
+
+@code{hg strip} is dangerous; for practical purposes it destroys
+history, and it also reverts the files in your workspace.  It's
+probably possible to recover the history, but I don't know how.  And any
+uncommitted changes that might be lost are gone forever.  However, it
+is useful in cases like this.
+
+When in doubt, use the safer method @ref{Q11.2.5}.
+
+
+@node Q11.2.7, , Q11.2.6, Bleeding Edge
+@unnumberedsubsec Testing patches with Mercurial Queues.
+
+When testing a patch proposed on xemacs-beta or xemacs-patches,
+conflicts or new heads often appear later, when using @code{hg pull -u}.
+
+There are both theoretical and practical reasons why this happens,
+and it's unlikely to change.  The current workflow of XEmacs is also
+unlikely to change soon; testing patches is also probably going to
+remain necessary.  One way to avoid this issue is to use Mercurial
+Queues (mq), an extension distributed with Mercurial.
+
+Enable mq by adding
+
+@example
+    [extensions]
+
+    hgext.mq =
+@end example
+
+to your @file{~/.hgrc}.  (Yes, the right hand side is empty.)  If you
+already have an @code{[extensions]} section, don't repeat it.  Add
+@code{hgext.mq =} to the existing extensions section.
+
+When you want to test a patch, you need an hg workspace with no
+uncommitted changes.  If you already have some uncommitted changes,
+you can preserve them with mq as follows:
+
+@example
+    $ hg qnew -f -m "Preserve local changes." local-changes
+@end example
+
+The @code{-m} flag specifies the commit message for the new patch.  The
+@code{-f} flag "forces" qnew to put all of the uncommitted local changes
+into an mq patch, and commits it (you will see a commit with summary
+"Preserve local changes." if you do an @code{hg log} now).
+"local-changes" is the name of the patch.
+
+Now, create an mq patch for the test patch (which we assume was saved
+to @file{/tmp/xemacs.patch}):
+
+    $ hg qimport -P -n test-xemacs-patch /tmp/xemacs.patch
+
+The @code{-n} flag specifies the name of the patch.  Give it a name
+sufficiently explicit so you'll know what it is later.  Remember, it
+may take several weeks for the patch to be pushed to the public
+mainline.  The @code{-P} flag says "apply this patch to the workspace
+now".
+
+When you want to update the workspace, you need to remove the mq
+commits, update, and restore your local changes and the test patch.
+You do it this way:
+
+@example
+    $ hg qpop --all
+    $ hg pull -u                # use your usual method, hg fetch etc.
+    $ hg qpush --all
+@end example
+
+@code{hg qpop --all} undoes all the mq commits, but leaves the patches
+in @file{.hg/patches}.  @code{hg qpush --all} reapplies the patches and
+restores the mq commits.  Of course you hope that the patch will be
+committed upstream.  When it is, you do this:
+
+@example
+    $ hg qpop --all
+    $ hg pull -u
+    $ hg qdelete test-xemacs-patch
+    $ hg qpush --all
+@end example
+
+and you're back in business with the official version of the patch you
+tested, and all your local changes applied.
+
+It's also possible to split your local changes into smaller mq
+patches, but that's out of scope for this answer.
+
 @bye