Cheaper branching under consideration?

[Magnus Therning]

On Tue, Aug 23, 2005 at 09:31:00AM +0100, Magnus Therning wrote:
>On Tue, Aug 23, 2005 at 09:51:07AM +0200, Jan Hudec wrote:
>>On Mon, Aug 22, 2005 at 23:00:09 +0100, Magnus Therning wrote:
>>> This might very well have been discussed already. Just thought I'd ask
>>> anyway.
>>> 
>>> Is cheaper branching, regarding space, being considered?
>>
>>Did you notice te threads mentioning centralized storage (plans)? There have
>>been at least two in last two days. In short, it should be possible to have
>>one common storage for several branches, so it would store all common
>>revisions just once. Would that fullfil your needs?
>
>It sure sounds like it would. I'll have to read through the thread.
>Thanks for the pointer.

Yes it will fulfill my needs.

However, until it's implemented I've cooked together a small plugin that
does a "shallow branch", a branch with only the last revision. Bzr seems
to work just fine, even though the revno is decreased to 1.

My idea was to use it to make micro-branching cheaper. (Also I wanted to
play with bzr :-)

/M

*** added file '.bzrignore'
--- /dev/null 
+++ .bzrignore 
@@ -0,0 +1,1 @@
+*.pyc

*** added file '__init__.py'
--- /dev/null 
+++ __init__.py 
@@ -0,0 +1,9 @@
+import bzrlib.commands
+
+import shallow_branch
+
+_commands = [shallow_branch.cmd_shallow_branch]
+
+if hasattr(bzrlib.commands, 'register_command'):
+    for cmd in _commands:
+        bzrlib.commands.register_command(cmd)

*** added file 'shallow_branch.py'
--- /dev/null 
+++ shallow_branch.py 
@@ -0,0 +1,47 @@
+from bzrlib.commands import Command
+
+class cmd_shallow_branch(Command):
+    '''Make a shallow branch.
+
+    A shallow branch is a branch without any history.
+
+    If TO_LOCATION is omitted, the last component of FROM_LOCATION will be
+    used. In other words, "shallow-branch ../foo/bar" will attempt to create
+    "./bar".
+
+    To retrieve a shallow branch of a particular revision, supply the
+    --revision parameter, as in "shallow-branch foo/bar --revision 5".
+    '''
+
+    takes_args = ['from_location', 'to_location?']
+    takes_options = ['revision']
+
+    def run(self, from_location, to_location=None, revision=[-1]):
+        import os
+        from bzrlib.branch import Branch
+        from bzrlib.merge import merge
+
+        if to_location == None:
+            to_location = os.path.basename(from_location.rstrip("/\\"))
+
+        try:
+            os.mkdir(to_location)
+        except OSError, e:
+            if e.errno == errno.EEXIST:
+                raise BzrCommandError('Target directory "%s" already'
+                        ' exists.' % to_location)
+            elif e.errno == errno.ENOENT:
+                raise BzrCommandError('Parent of "%s" does not exist.'
+                        % to_location)
+            else:
+                raise
+
+        br_to = Branch(to_location, init=True)
+        br_from = Branch(from_location)
+
+        revno, rev_id = br_from.get_revision_info(revision[0])
+        br_to.install_revisions(br_from, [rev_id], None)
+        br_to.append_revision(rev_id)
+
+        merge((to_location, -1), (to_location, None),
+                this_dir=to_location, check_clean=False)


-- 
Magnus Therning                    (OpenPGP: 0xAB4DFBA4)
magnus at therning.org
http://therning.org/magnus

Software is not manufactured, it is something you write and publish.
Keep Europe free from software patents, we do not want censorship
by patent law on written works.

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1000 miles away, and the government disagrees with that. GQ [magazine
in England] quoted me on that -- they changed one letter. It said I
should be able to whisper something in your *car*, even though I am
1000 miles away. I wonder what the people in England think of me.
      -- Philip Zimmermann
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