Re: Switching branches without committing changes

Thanks all for the great info!  The scenarios you describe, Junio,  
make perfect sense.  In fact, that's pretty much the way I think when  
I'm coding and decided to branch or not to branch (that is the  
question).  Along the lines of those scenarios (maybe this should be a  
separate post), are there any guidelines or best practices on when/if  
to sync your branches with master (hope that's not a stupid question,  
I'm still learning)?

-Joe

On Mar 21, 2008, at 12:42 AM, Junio C Hamano wrote:

Jeff King [off-list ref] writes:

quoted

On Fri, Mar 21, 2008 at 12:06:47AM -0400, Shawn O. Pearce wrote:

quoted

Use `git checkout -m` to switch the branch anyway.  However, if
there is a merge conflict while you are trying to carry the changes
to the other branch you may be faced with a merge conflict you are
not prepared to resolve, or simply cannot resolve in a reasonable
period of time.

Ah, for some reason I didn't think of '-m' in the advice I gave (I  
guess
I have just never used it). It is almost certainly simpler than  
using a
'stash' at this point (but I do think stashing _beforehand_ still has
advantages).

The thing is, that -m is really to mollify people who are _too_  
accustomed
to CVS/SVN update behaviour.  Over there, "scm update" does not give  
you
any choice other than having to merge.

With git, stashing or creating Park commits are very cheap operation  
and
unless you are reasonably sure that your local changes do not conflict
with the branch you are switching to, there is no strong reason to  
prefer
"checkout -m".

Switching branches with dirty state can have three scenarios:

(1) you are getting interrupted and your current local changes do not
    belong to what you are going to commit after switching (e.g. "the
    boss says fix that right away").

    recommendation: stash, or Park commit

(2) you have started working but realized what you are working on  
belongs
    to a new topic.

    recommendation: checkout -b

(3) you have started working but realized what you are working on  
belongs
    to an existing topic.

    recommendation: checkout -m

In case (1), if the change is small, trivial or independent from  
what you
are switching branches to work on, you can "git checkout" (if the  
change
is about an unrelated thing, hopefully there won't be any overlap at  
the
file level) or "git checkout -m" (again, if the change is about an
unrelated thing, the merge hopefully would be trivial) to switch  
branches,
perform the unrelated change and commit only that unrelated change,  
and
"git checkout" (or "git checkout -m") to come back to where you  
started.
But if you had to use "-m" when switching branches, that means the  
change
you need to commit in the switched branch may have to include some  
changes
you will do to that modified file, and you would need per-hunk  
commit with
"git add -i" to exclude existing changes.  In such a case, stashing  
the
local changes away before branch switching would be much easier  
workflow.

In case (2), the solution is always "checkout -b".  There is no other
choice.

In case (3), the solution is always "checkout -m".  Stashing,  
switching
and then unstashing will give the same conflicts as "checkout -m"  
would
give you, and the change you were working on has to be done on that
switched to branch, so there is no escaping from conflict resolution,
unless you are willing to redo your change on the breanch you  
switched to
again.