diff options
Diffstat (limited to 'Annex')
| -rw-r--r-- | Annex/Branch.hs | 88 |
1 files changed, 65 insertions, 23 deletions
diff --git a/Annex/Branch.hs b/Annex/Branch.hs index 4c3192f53..0095b586b 100644 --- a/Annex/Branch.hs +++ b/Annex/Branch.hs @@ -117,28 +117,30 @@ commit message = whenM journalDirty $ lockJournal $ do g <- gitRepo withIndex $ liftIO $ Git.commit g message fullname [fullname] -{- Ensures that the branch is up-to-date; should be called before - - data is read from it. Runs only once per git-annex run. +{- Ensures that the branch is up-to-date; should be called before data is + - read from it. Runs only once per git-annex run. - - - Before refs are merged into the index, it's - - important to first stage the journal into the - - index. Otherwise, any changes in the journal - - would later get staged, and might overwrite - - changes made during the merge. + - Before refs are merged into the index, it's important to first stage the + - journal into the index. Otherwise, any changes in the journal would + - later get staged, and might overwrite changes made during the merge. - - - It would be cleaner to handle the merge by - - updating the journal, not the index, with changes - - from the branches. + - It would be cleaner to handle the merge by updating the journal, not the + - index, with changes from the branches. + - + - The index is always updated using a union merge, as that's the most + - efficient way to update it. However, if the branch can be + - fast-forwarded, that is then done, rather than adding an unnecessary + - commit to it. -} update :: Annex () update = onceonly $ do + g <- gitRepo -- check what needs updating before taking the lock dirty <- journalDirty - c <- filterM changedbranch =<< siblingBranches + c <- filterM (changedBranch name . snd) =<< siblingBranches let (refs, branches) = unzip c unless (not dirty && null refs) $ withIndex $ lockJournal $ do when dirty stageJournalFiles - g <- gitRepo unless (null branches) $ do showSideAction $ "merging " ++ (unwords $ map Git.refDescribe branches) ++ @@ -150,24 +152,64 @@ update = onceonly $ do - modify the branch. -} liftIO $ Git.UnionMerge.merge_index g branches - liftIO $ Git.commit g "update" fullname (nub $ fullname:refs) + ff <- if dirty then return False else tryFastForwardTo refs + unless ff $ + liftIO $ Git.commit g "update" fullname (nub $ fullname:refs) invalidateCache where - changedbranch (_, branch) = do - g <- gitRepo - -- checking with log to see if there have been changes - -- is less expensive than always merging - diffs <- liftIO $ Git.pipeRead g [ - Param "log", - Param (name ++ ".." ++ branch), - Params "--oneline -n1" - ] - return $ not $ L.null diffs onceonly a = unlessM (branchUpdated <$> getState) $ do r <- a disableUpdate return r +{- Checks if the second branch has any commits not present on the first + - branch. -} +changedBranch :: String -> String -> Annex Bool +changedBranch origbranch newbranch = do + g <- gitRepo + diffs <- liftIO $ Git.pipeRead g [ + Param "log", + Param (origbranch ++ ".." ++ newbranch), + Params "--oneline -n1" + ] + return $ not $ L.null diffs + +{- Given a set of refs that are all known to have commits not + - on the git-annex branch, tries to update the branch by a + - fast-forward. + - + - In order for that to be possible, one of the refs must contain + - every commit present in all the other refs, as well as in the + - git-annex branch. + -} +tryFastForwardTo :: [String] -> Annex Bool +tryFastForwardTo [] = return True +tryFastForwardTo (first:rest) = do + -- First, check that the git-annex branch does not contain any + -- new commits that are in the first other branch. If it does, + -- cannot fast-forward. + diverged <- changedBranch first fullname + if diverged + then no_ff + else maybe no_ff do_ff =<< findbest first rest + where + no_ff = return False + do_ff branch = do + g <- gitRepo + liftIO $ Git.run g "update-ref" [Param fullname, Param branch] + return True + findbest c [] = return $ Just c + findbest c (r:rs) + | c == r = findbest c rs + | otherwise = do + better <- changedBranch c r + worse <- changedBranch r c + case (better, worse) of + (True, True) -> return Nothing -- divergent fail + (True, False) -> findbest r rs -- better + (False, True) -> findbest c rs -- worse + (False, False) -> findbest c rs -- same + {- Avoids updating the branch. A useful optimisation when the branch - is known to have not changed, or git-annex won't be relying on info - from it. -} |