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  • Junio C Hamano's avatar
    Multi-backend merge driver. · 91063bbc
    Junio C Hamano authored 
    

The new command 'git merge' takes the current head and one or more
remote heads, with the commit log message for the automated case.

If the heads being merged are simple fast-forwards, it acts the
same way as the current 'git resolve'.  Otherwise, it tries
different merge strategies and takes the result from the one that
succeeded auto-merging, if there is any.

If no merge strategy succeeds auto-merging, their results are
evaluated for number of paths needed for hand resolving, and the
one with the least number of such paths is left in the working
tree.  The user is asked to resolve them by hand and make a
commit manually.

The calling convention from the 'git merge' driver to merge
strategy programs is very simple:

 - A strategy program is to be called 'git-merge-<strategy>'.

 - They take input of this form:

	<common1> <common2> ... '--' <head> <remote1> <remote2>...

   That is, one or more the common ancestors, double dash, the
   current head, and one or more remote heads being merged into
   the current branch.

 - Before a strategy program is called, the working tree is
   matched to the current <head>.

 - The strategy program exits with status code 0 when it
   successfully auto-merges the given heads.  It should do
   update-cache for all the merged paths when it does so -- the
   index file will be used to record the merge result as a
   commit by the driver.

 - The strategy program exits with status code 1 when it leaves
   conflicts behind.  It should do update-cache for all the
   merged paths that it successfully auto-merged, and leave the
   cache entry in the index file as the same as <head> for paths
   it could not auto-merge, and leave its best-effort result
   with conflict markers in the working tree when it does so.

 - The strategy program exists with status code other than 0 or
   1 if it does not handle the given merge at all.

As examples, this commit comes with merge strategies based on
'git resolve' and 'git octopus'.

Signed-off-by: default avatarJunio C Hamano <junkio@cox.net>
    91063bbc