Turn off file content merge on pull/merge

[Andrew Bennetts]

Michael Baytalsky wrote:
> 
> Using bazaar 2.1.0 on windows.
> 
> Is it possible to completely disable any content merging by bazaar?
> 
> I'd very much prefer if it would require me to merge manually if ANY
> conflict in the content occurs. We had some problems recently with
> it merging automatically two corrected files resulting in loosing
> my local tested copy of work - because instead of reporting a
> conflict it merged in somebody's else changes, which partly
> duplicated my work.
> 
> There's no way to tell it NOT to merge contents of text files during
> pull and this is sort of scary, because it require to check manually
> the content of all pulled files which were automatically merged.
> 
> Also, I've seen a couple of articles recently on how 3-way merging
> can be harmful. So... would be nice to be able to turn it off completely.

Not builtin, but here's a plugin that should turn it off:

---- conservative_merge.py ----
"""Always conflict if both branches have changed a file (avoiding 3-way merge,
etc).

Requires Bazaar 2.1.0 or newer.
"""

from bzrlib.merge import AbstractPerFileMerger, Merger

def conservative_merge_hook(merger):
    """Hook to disable 3-way merge."""
    return AlwaysConflictMerger(merger)

class AlwaysConflictMerger(AbstractPerFileMerger):

    def __init__(self, merger):
        AbstractPerFileMerger.__init__(self, merger)
        self._enabled = None

    def merge_contents(self, params):
        """Merge the contents of a single file."""
        # First, should this custom merge logic be used?
        if not self.conservative_enabled():
            # Not enabled for this branch
            return 'not_applicable', None
        elif params.winner == 'other':
            # Only changed in OTHER branch, default behaviour is fine.
            return 'not_applicable', None
        elif not params.is_file_merge():
            # THIS and OTHER aren't both files
            return 'not_applicable', None
        return 'conflicted', params.this_lines
    
    def conservative_enabled(self):
        if self._enabled is None:
            config = self.merger.this_branch.get_config()
            option = config.get_user_option_as_bool('conservative_merge')
            if option is None:
                # Default to false
                option = False
            self._enabled = option
        return self._enabled

Merger.hooks.install_named_hook(
    'merge_file_content', conservative_merge_hook, 'conservative file merge')
---- END ----

To use that,

 1) Put that file in your plugins directory (see e.g.
    <http://doc.bazaar.canonical.com/plugins/en/plugin-installation.html#per-user-installation>)
 2) set "conservative_merge = true" in your configuration somewhere, e.g. in
    your locations.conf

You may also be interested in
<https://answers.edge.launchpad.net/bzr/+question/103163>, which has a similar
plugin that does the same for specific file extensions in all branches (rather
than for all files in configured branches).

-Andrew.