bzr pull vs bzr merge

bazaar, version-control

Solution

Note that I didn't make any local changes. Is `bzr pull` the recommended way?

Yes, it sounds like `bzr pull` is the appropriate command for your use. `pull` takes a remote source branch and copies any changes from it to a local destination branch at an older revision. (I use "remote" and "local" here to mean "source" and "destination." Any two branches will do, even two local branches.)

remote: A --> B --> C --> D
         \                 \
       (branch)           (pull)
           \                  \
local:      \--> A (no change) \--> D

A `pull` only works if the two branches haven't diverged, i.e., if the revision of the destination is an old revision of the source. `push` is just the opposite operation: it copies changes in a local branch to remote branch at an older revision.

remote: A      (no change)       --> C
         \                      /
       (branch)             (push)
           \                  /
local:      \--> A --> B --> C

A `merge` is used when you want to copy changes to a local branch that has diverged from the remote branch.

remote: A --> B --> C --> D
         \                 \  
       (branch)           (merge) 
           \                  \ 
local:      \--> A --> X --> Y --> Z

Here, `Z` includes all of the changes from `D` and the changes from `Y`. A `pull` is not possible in this case. Note that you must `commit` after a `merge` in order to save the new merged revision, whereas a pull automatically brings the branch to a saved revision point.

A `checkout` allows you to use bzr in a mode that is similar to CVS/SVN: the local branch will be "attached" to a remote branch; `commit`s will be automatically `push`ed; if the remote branch has diverged, the commit will fail; an `update` is just a `merge` from the "attached" remote branch.

Problem

I'm using bzr for a very simple task: getting the development version of GNU Emacs. After the initial `bzr branch`, I'd like to keep my local version up to date. I read about the documentation on `bzr pull` and `bzr merge`, but couldn't make sense out of it. I tried `bzr merge` for a few days, and found that `bzr merge` often resulted in unresolvable conflicts. Note that I didn't make any local changes. Is `bzr pull` the recommended way? EDIT 1 (added a diagram stolen from Chris Conway): ``` remote: A --> B --> C --> D \ \ (branch) (merge) \ \ local: \--> A (no change) \--> why conflicts? ``` I understand git and darcs, but have no knowledge about bzr. Analogies to git or darcs will help a lot. EDIT 2: Is `update` supposed to work with `checkout` only? Doing an `update` in a `branch` doesn't seem to do anything.

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