import ctm (current through mail)

for more see http://www.openbsd.org/ctm.html - it's basicaly the FreeBSD
version adapted to OpenBSD - i'll bring in the latest FreeBSD changes in the
next days

1 files changed, 97 insertions, 0 deletions

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+# ----------------------------------------------------------------------------
+# "THE BEER-WARE LICENSE" (Revision 42):
+# <phk@login.dknet.dk> wrote this file.  As long as you retain this notice you
+# can do whatever you want with this stuff. If we meet some day, and you think
+# this stuff is worth it, you can buy me a beer in return.   Poul-Henning Kamp
+# ----------------------------------------------------------------------------
+#
+# $Id: README,v 1.1 1996/10/30 17:32:57 graichen Exp $
+#
+
+What will I not find in this file ?
+-----------------------------------
+Instructions on how to obtain FreeBSD via CTM.
+Contact <phk@freefall.cdrom.com> for that.
+
+What is CTM ?
+-------------
+CTM was originally "Cvs Through eMail", but has since changed scope to be
+much more general.
+CTM is now meant to be the definitive way to make and apply a delta between
+two versions of a directory tree.
+There are two parts to this, making the delta and applying it.  These are two
+entirely different things.  CTM concentrates the computation-burden on the
+generation og the deltas, as a delta very often is applied more times than
+it is made.  Second CTM tries to make the minimal size delta.
+
+Why not use diff/patch ?
+------------------------
+Good question.  Primarily because diff and patch doesn't do their job very 
+well.  They don't deal with binary files (in this case files with '\0' or 
+'\0377' characters in them or files that doesn't end in '\n') which isn't
+a big surprise:  they were made to deal with text-files only.  As a second
+gripe, with patch you send the entire file to delete it.  Not particular
+efficient.
+
+So what does CTM do exactly ?
+-----------------------------
+CTM will produce a file, (a delta) containing the instructions and data needed
+to take another copy of the tree from the old to the new status.  CTM means to
+do this in the exact sense, and therefore the delta contains MD5 checksums to
+verify that the tree it is applied to is indeed in the state CTM expects.
+
+This means that if you have modified the tree locally, CTM might not be able
+to upgrade your copy.
+
+How do I make a CTM-delta ?
+---------------------------
+Don't.  Send me email before you even try.  This is yet not quite as trivial
+as I would like.  This is not to discourage you from using CTM, it is merely
+to warn you that it is slightly tedious and takes much diskspace.
+
+How do I apply a CTM-delta ?
+----------------------------
+You pass it to the 'ctm' command.  You can pass a CTM-delta on stdin, or
+you can give the filename as an argument.  If you do the latter, you make
+life a lot easier for your self, since the program can accept gzip'ed files
+and since it will not have to make a temporary copy of your file.  You can
+specify multiple deltas at one time, they will be proccessed one at a time.
+
+The ctm command runs in a number of passes.  It will process the entire
+input file in each pass, before commencing with the next pass.
+
+Pass 1 will validate that the input file is OK.  The syntax, the data and 
+the global MD5 checksum will be checked.  If any of these fail, ctm will
+never be able to do anything with the file, so it will simply reject it.
+
+Pass 2 will validate that the directory tree is in the state expected by
+the CTM-delta.  This is done by looking for files and directories which
+should/should not exists and by checking the MD5 checksums of files.  
+
+Pass 3 will actually apply the delta.
+
+Should I delete the delta when I have applied it ?
+--------------------------------------------------
+No.  You might want to selectively reconstruct a file latter on.
+
+What features are are planned ?
+-------------------------------
+This list isn't exhaustive, and it isn't sorted in priority.
+	Reconstruct subset of tree.
+	Make tar-copy of things which will be affected.
+	Verify.
+	Internal editor instead of ed(1)
+	Support for mode
+	Support for uid/gid
+	Support for hardlinks
+	Support for symlinks
+
+Isn't this a bit thin yet ?
+---------------------------
+Yes.
+
+Can I say something ?
+---------------------
+Yes, email me: <phk@freefall.cdrom.com>
+
+Poul-Henning