patch-2.4.20 linux-2.4.20/Documentation/BK-usage/bk-kernel-howto.txt

• Lines: 276
• Date: Thu Nov 28 15:53:08 2002
• Orig file: linux-2.4.19/Documentation/BK-usage/bk-kernel-howto.txt
• Orig date: Wed Dec 31 16:00:00 1969

diff -urN linux-2.4.19/Documentation/BK-usage/bk-kernel-howto.txt linux-2.4.20/Documentation/BK-usage/bk-kernel-howto.txt
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+
+		   Doing the BK Thing, Penguin-Style
+
+
+
+
+This set of notes is intended mainly for kernel developers, occasional
+or full-time, but sysadmins and power users may find parts of it useful
+as well.  It assumes at least a basic familiarity with CVS, both at a
+user level (use on the cmd line) and at a higher level (client-server model).
+Due to the author's background, an operation may be described in terms
+of CVS, or in terms of how that operation differs from CVS.
+
+This is -not- intended to be BitKeeper documentation.  Always run
+"bk help <command>" or in X "bk helptool <command>" for reference
+documentation.
+
+
+BitKeeper Concepts
+------------------
+
+In the true nature of the Internet itself, BitKeeper is a distributed
+system.  When applied to revision control, this means doing away with
+client-server, and changing to a parent-child model... essentially
+peer-to-peer.  On the developer's end, this also represents a
+fundamental disruption in the standard workflow of changes, commits,
+and merges.  You will need to take a few minutes to think about
+how to best work under BitKeeper, and re-optimize things a bit.
+In some sense it is a bit radical, because it might described as
+tossing changes out into a maelstrom and having them magically
+land at the right destination... but I'm getting ahead of myself.
+
+Let's start with this progression:
+Each BitKeeper source tree on disk is a repository unto itself.
+Each repository has a parent.
+Each repository contains a set of a changesets ("csets").
+Each cset is one or more changed files, bundled together.
+
+Each tree is a repository, so all changes are checked into the local
+tree.  When a change is checked in, all modified files are grouped
+into a logical unit, the changeset.  Internally, BK links these
+changesets in a tree, representing various converging and diverging
+lines of development.  These changesets are the bread and butter of
+the BK system.
+
+After the concept of changesets, the next thing you need to get used
+to is having multiple copies of source trees lying around.  This -really-
+takes some getting used to, for some people.  Separate source trees
+are the means in BitKeeper by which you delineate parallel lines
+of development, both minor and major.  What would be branches in
+CVS become separate source trees, or "clones" in BitKeeper [heh,
+or Star Wars] terminology.
+
+Clones and changesets are the tools from which most of the power of
+BitKeeper is derived.  As mentioned earlier, each clone has a parent,
+the tree used as the source when the new clone was created.  In a
+CVS-like setup, the parent would be a remote server on the Internet,
+and the child is your local clone of that tree.
+
+Once you have established a common baseline between two source trees --
+a common parent -- then you can merge changesets between those two
+trees with ease.  Merging changes into a tree is called a "pull", and
+is analagous to 'cvs update'.  A pull downloads all the changesets in
+the remote tree you do not have, and merges them.  Sending changes in
+one tree to another tree is called a "push".  Push sends all changes
+in the local tree the remote does not yet have, and merges them.
+
+From these concepts come some initial command examples:
+
+1) bk clone -q http://linux.bkbits.net/linux-2.5 linus-2.5
+Download a 2.5 stock kernel tree, naming it "linus-2.5" in the local dir.
+The "-q" disables listing every single file as it is downloaded.
+
+2) bk clone -ql linus-2.5 alpha-2.5
+Create a separate source tree for the Alpha AXP architecture.
+The "-l" uses hard links instead of copying data, since both trees are
+on the local disk.  You can also replace the above with "bk lclone -q ..."
+
+You only clone a tree -once-.  After cloning the tree lives a long time
+on disk, being updating by pushes and pulls.
+
+3) cd alpha-2.5 ; bk pull http://gkernel.bkbits.net/alpha-2.5
+Download changes in "alpha-2.5" repository which are not present
+in the local repository, and merge them into the source tree.
+
+4) bk -r co -q
+Because every tree is a repository, files must be checked out before
+they will be in their standard places in the source tree.
+
+5)	bk vi fs/inode.c				# example change...
+	bk citool					# checkin, using X tool
+	bk push bk://gkernel@bkbits.net/alpha-2.5	# upload change
+Typical example of a BK sequence that would replace the analagous CVS
+situation,
+	vi fs/inode.c
+	cvs commit
+
+As this is just supposed to be a quick BK intro, for more in-depth
+tutorials, live working demos, and docs, see http://www.bitkeeper.com/
+
+
+
+BK and Kernel Development Workflow
+----------------------------------
+Currently the latest 2.5 tree is available via "bk clone $URL"
+and "bk pull $URL" at http://linux.bkbits.net/linux-2.5
+This should change in a few weeks to a kernel.org URL.
+
+
+A big part of using BitKeeper is organizing the various trees you have
+on your local disk, and organizing the flow of changes among those
+trees, and remote trees.  If one were to graph the relationships between
+a desired BK setup, you are likely to see a few-many-few graph, like
+this:
+
+		    linux-2.5
+		        |
+	       merge-to-linus-2.5
+		 /    |      |
+	        /     |      |
+	vm-hacks  bugfixes  filesys   personal-hacks
+	      \	      |	     |		/
+	       \      |      |         /
+		\     |      |        /
+	         testing-and-validation
+
+Since a "bk push" sends all changes not in the target tree, and
+since a "bk pull" receives all changes not in the source tree, you want
+to make sure you are only pushing specific changes to the desired tree,
+not all changes from "peer parent" trees.  For example, pushing a change
+from the testing-and-validation tree would probably be a bad idea,
+because it will push all changes from vm-hacks, bugfixes, filesys, and
+personal-hacks trees into the target tree.
+
+One would typically work on only one "theme" at a time, either
+vm-hacks or bugfixes or filesys, keeping those changes isolated in
+their own tree during development, and only merge the isolated with
+other changes when going upstream (to Linus or other maintainers) or
+downstream (to your "union" trees, like testing-and-validation above).
+
+It should be noted that some of this separation is not just recommended
+practice, it's actually [for now] -enforced- by BitKeeper.  BitKeeper
+requires that changesets maintain a certain order, which is the reason
+that "bk push" sends all local changesets the remote doesn't have.  This
+separation may look like a lot of wasted disk space at first, but it
+helps when two unrelated changes may "pollute" the same area of code, or
+don't follow the same pace of development, or any other of the standard
+reasons why one creates a development branch.
+
+Small development branches (clones) will appear and disappear:
+
+	-------- A --------- B --------- C --------- D -------
+	          \                                 /
+		   -----short-term devel branch-----
+
+While long-term branches will parallel a tree (or trees), with period
+merge points.  In this first example, we pull from a tree (pulls,
+"\") periodically, such as what occurs when tracking changes in a
+vendor tree, never pushing changes back up the line:
+
+	-------- A --------- B --------- C --------- D -------
+	          \                       \           \
+	           ----long-term devel branch-----------------
+
+And then a more common case in Linux kernel development, a long term
+branch with periodic merges back into the tree (pushes, "/"):
+
+	-------- A --------- B --------- C --------- D -------
+	          \                       \         / \
+	           ----long-term devel branch-----------------
+
+
+
+
+
+Submitting Changes to Linus
+---------------------------
+There's a bit of an art, or style, of submitting changes to Linus.
+Since Linus's tree is now (you might say) fully integrated into the
+distributed BitKeeper system, there are several prerequisites to
+properly submitting a BitKeeper change.  All these prereq's are just
+general cleanliness of BK usage, so as people become experts at BK, feel
+free to optimize this process further (assuming Linus agrees, of
+course).
+
+
+
+0) Make sure your tree was originally cloned from the linux-2.5 tree
+created by Linus.  If your tree does not have this as its ancestor, it
+is impossible to reliably exchange changesets.
+
+
+
+1) Pay attention to your commit text.  The commit message that
+accompanies each changeset you submit will live on forever in history,
+and is used by Linus to accurately summarize the changes in each
+pre-patch.  Remember that there is no context, so
+	"fix for new scheduler changes"
+would be too vague, but
+	"fix mips64 arch for new scheduler switch_to(), TIF_xxx semantics"
+would be much better.
+
+You can and should use the command "bk comment -C<rev>" to update the
+commit text, and improve it after the fact.  This is very useful for
+development: poor, quick descriptions during development, which get
+cleaned up using "bk comment" before issuing the "bk push" to submit the
+changes.
+
+
+
+2) Include an Internet-available URL for Linus to pull from, such as
+
+	Pull from:  http://gkernel.bkbits.net/net-drivers-2.5
+
+
+
+3) Include a summary and "diffstat -p1" of each changeset that will be
+downloaded, when Linus issues a "bk pull".  The author auto-generates
+these summaries using "bk push -nl <parent> 2>&1", to obtain a listing
+of all the pending-to-send changesets, and their commit messages.
+
+It is important to show Linus what he will be downloading when he issues
+a "bk pull", to reduce the time required to sift the changes once they
+are downloaded to Linus's local machine.
+
+IMPORTANT NOTE:  One of the features of BK is that your repository does
+not have to be up to date, in order for Linus to receive your changes.
+It is considered a courtesy to keep your repository fairly recent, to
+lessen any potential merge work Linus may need to do.
+
+
+4) Split up your changes.  Each maintainer<->Linus situation is likely
+to be slightly different here, so take this just as general advice.  The
+author splits up changes according to "themes" when merging with Linus.
+Simultaneous pushes from local development go to special trees which
+exist solely to house changes "queued" for Linus.  Example of the trees:
+
+	net-drivers-2.5 -- on-going net driver maintenance
+	vm-2.5 -- VM-related changes
+	fs-2.5 -- filesystem-related changes
+
+Linus then has much more freedom for pulling changes.  He could (for
+example) issue a "bk pull" on vm-2.5 and fs-2.5 trees, to merge their
+changes, but hold off net-drivers-2.5 because of a change that needs
+more discussion.
+
+Other maintainers may find that a single linus-pull-from tree is
+adequate for passing BK changesets to him.
+
+
+
+Frequently Answered Questions
+-----------------------------
+1) How do I change the e-mail address shown in the changelog?
+A. When you run "bk citool" or "bk commit", set environment
+   variables BK_USER and BK_HOST to the desired username
+   and host/domain name.
+
+
+2) How do I use tags / get a diff between two kernel versions?
+A. Pass the tags Linus uses to 'bk export'.
+
+ChangeSets are in a forward-progressing order, so it's pretty easy
+to get a snapshot starting and ending at any two points in time.
+Linus puts tags on each release and pre-release, so you could use
+these two examples:
+
+    bk export -tpatch -hdu -rv2.5.4,v2.5.5 | less
+        # creates patch-2.5.5 essentially
+    bk export -tpatch -du -rv2.5.5-pre1,v2.5.5 | less
+        # changes from pre1 to final
+
+A tag is just an alias for a specific changeset... and since changesets
+are ordered, a tag is thus a marker for a specific point in time (or
+specific state of the tree).