aboutsummaryrefslogtreecommitdiff
path: root/Annex/Branch.hs
blob: 0ac41999449a07c876db5a7ba62a2a1266239ed6 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
{- management of the git-annex branch
 -
 - Copyright 2011 Joey Hess <joey@kitenet.net>
 -
 - Licensed under the GNU GPL version 3 or higher.
 -}

module Annex.Branch (
	create,
	update,
	disableUpdate,
	get,
	change,
	commit,
	files,
	refExists,
	hasOrigin,
	hasSomeBranch,
	name	
) where

import System.IO.Binary
import System.Exit
import qualified Data.ByteString.Lazy.Char8 as L

import Common.Annex
import Annex.Exception
import Types.BranchState
import qualified Git
import qualified Git.UnionMerge
import qualified Annex
import Annex.CatFile

{- Name of the branch that is used to store git-annex's information. -}
name :: Git.Ref
name = Git.Ref "git-annex"

{- Fully qualified name of the branch. -}
fullname :: Git.Ref
fullname = Git.Ref $ "refs/heads/" ++ show name

{- Branch's name in origin. -}
originname :: Git.Ref
originname = Git.Ref $ "origin/" ++ show name

{- Populates the branch's index file with the current branch contents.
 - 
 - This is only done when the index doesn't yet exist, and the index 
 - is used to build up changes to be commited to the branch, and merge
 - in changes from other branches.
 -}
genIndex :: Git.Repo -> IO ()
genIndex g = Git.UnionMerge.stream_update_index g
	[Git.UnionMerge.ls_tree fullname g]

{- Merges the specified branches into the index.
 - Any changes staged in the index will be preserved. -}
mergeIndex :: [Git.Ref] -> Annex ()
mergeIndex branches = do
	h <- catFileHandle
	inRepo $ \g -> Git.UnionMerge.merge_index h g branches

{- Runs an action using the branch's index file. -}
withIndex :: Annex a -> Annex a
withIndex = withIndex' False
withIndex' :: Bool -> Annex a -> Annex a
withIndex' bootstrapping a = do
	f <- fromRepo gitAnnexIndex
	bracketIO (Git.useIndex f) id $ do
		unlessM (liftIO $ doesFileExist f) $ do
			unless bootstrapping create
			liftIO $ createDirectoryIfMissing True $ takeDirectory f
			unless bootstrapping $ inRepo genIndex
		a

{- Updates the branch's index to reflect the current contents of the branch.
 - Any changes staged in the index will be preserved.
 -
 - Compares the ref stored in the lock file with the current
 - ref of the branch to see if an update is needed.
 -}
updateIndex :: Annex (Maybe Git.Ref)
updateIndex = do
	branchref <- getRef fullname
	go branchref
	return branchref
	where
		go Nothing = return ()
		go (Just branchref) = do
			lock <- fromRepo gitAnnexIndexLock
			lockref <- firstRef <$> liftIO (catchDefaultIO (readFileStrict lock) "")
			when (lockref /= branchref) $ do
				withIndex $ mergeIndex [fullname]
				setIndexRef branchref

{- Record that the branch's index has been updated to correspond to a
 - given ref of the branch. -}
setIndexRef :: Git.Ref -> Annex ()
setIndexRef ref = do
        lock <- fromRepo gitAnnexIndexLock
	liftIO $ writeFile lock $ show ref ++ "\n"

{- Commits the staged changes in the index to the branch.
 - 
 - Ensures that the branch's index file is first updated to include the
 - current state of the branch, before running the commit action. This
 - is needed because the branch may have had changes pushed to it, that
 - are not yet reflected in the index.
 -
 - Also safely handles a race that can occur if a change is being pushed
 - into the branch at the same time. When the race happens, the commit will
 - be made on top of the newly pushed change, but without the index file
 - being updated to include it. The result is that the newly pushed
 - change is reverted. This race is detected and another commit made
 - to fix it.
 -}
commitBranch :: String -> [Git.Ref] -> Annex ()
commitBranch message parents = do
	expected <- updateIndex
	committedref <- inRepo $ Git.commit message fullname parents
	setIndexRef committedref
	parentrefs <- commitparents <$> catObject committedref
	when (racedetected expected parentrefs) $
		fixrace committedref parentrefs
	where
		-- look for "parent ref" lines and return the refs
		commitparents = map (Git.Ref . snd) . filter isparent .
			map (toassoc . L.unpack) . L.lines
		toassoc = separate (== ' ')
		isparent (k,_) = k == "parent"
		
 		{- The race can be detected by checking the commit's
		 - parent, which will be the newly pushed branch,
		 - instead of the expected ref that the index was updated to. -}
		racedetected Nothing parentrefs
			| null parentrefs = False -- first commit, no parents
			| otherwise = True -- race on first commit
		racedetected (Just expectedref) parentrefs
			| expectedref `elem` parentrefs = False -- good parent
			| otherwise = True -- race!
		
		{- To recover from the race, union merge the lost refs
		 - into the index, and recommit on top of the bad commit. -}
		fixrace committedref lostrefs = do
			mergeIndex lostrefs
			commitBranch racemessage [committedref]
		
		racemessage = message ++ " (recovery from race)"

{- Runs an action using the branch's index file, first making sure that
 - the branch and index are up-to-date. -}
withIndexUpdate :: Annex a -> Annex a
withIndexUpdate a = update >> withIndex a

getState :: Annex BranchState
getState = Annex.getState Annex.branchstate

setState :: BranchState -> Annex ()
setState state = Annex.changeState $ \s -> s { Annex.branchstate = state }

setCache :: FilePath -> String -> Annex ()
setCache file content = do
	state <- getState
	setState state { cachedFile = Just file, cachedContent = content }

invalidateCache :: Annex ()
invalidateCache = do
	state <- getState
	setState state { cachedFile = Nothing, cachedContent = "" }

getCache :: FilePath -> Annex (Maybe String)
getCache file = getState >>= go
	where
		go state
			| cachedFile state == Just file =
				return $ Just $ cachedContent state
			| otherwise = return Nothing

{- Creates the branch, if it does not already exist. -}
create :: Annex ()
create = unlessM hasBranch $ hasOrigin >>= go
	where
		go True = do
			inRepo $ Git.run "branch"
				[Param $ show name, Param $ show originname]
			maybe (return ()) setIndexRef =<< getRef fullname
		go False = withIndex' True $ 
			setIndexRef =<< (inRepo $ Git.commit "branch created" fullname [])

{- Stages the journal, and commits staged changes to the branch. -}
commit :: String -> Annex ()
commit message = whenM journalDirty $ lockJournal $ do
	stageJournalFiles
	withIndex $ commitBranch message [fullname]

{- Ensures that the branch and index are 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.
 -
 - (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
	-- ensure branch exists, and index is up-to-date
	create
	_ <- updateIndex
	-- check what needs updating before taking the lock
	dirty <- journalDirty
	c <- filterM (changedBranch name . snd) =<< siblingBranches
	let (refs, branches) = unzip c
	unless (not dirty && null refs) $ withIndex $ lockJournal $ do
		when dirty stageJournalFiles
		let merge_desc = if null branches
			then "update" 
			else "merging " ++
				unwords (map Git.refDescribe branches) ++ 
				" into " ++ show name
		unless (null branches) $ do
			showSideAction merge_desc
			mergeIndex branches
		ff <- if dirty then return False else tryFastForwardTo refs
		unless ff $ commitBranch merge_desc (nub $ fullname:refs)
		invalidateCache
	where
		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 :: Git.Branch -> Git.Branch -> Annex Bool
changedBranch origbranch newbranch = not . L.null <$> diffs
	where
		diffs = inRepo $ Git.pipeRead
			[ Param "log"
			, Param (show origbranch ++ ".." ++ show newbranch)
			, Params "--oneline -n1"
			]

{- 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 :: [Git.Ref] -> Annex Bool
tryFastForwardTo [] = return True
tryFastForwardTo (first:rest) = do
	-- First, check that the git-annex branch does not contain any
	-- new commits that are not 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
			inRepo $ Git.run "update-ref"
				[Param $ show fullname, Param $ show 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. -}
disableUpdate :: Annex ()
disableUpdate = Annex.changeState setupdated
	where
		setupdated s = s { Annex.branchstate = new }
			where
				new = old { branchUpdated = True }
				old = Annex.branchstate s

{- Checks if a git ref exists. -}
refExists :: Git.Ref -> Annex Bool
refExists ref = inRepo $ Git.runBool "show-ref"
	[Param "--verify", Param "-q", Param $ show ref]

{- Does the main git-annex branch exist? -}
hasBranch :: Annex Bool
hasBranch = refExists fullname

{- Does origin/git-annex exist? -}
hasOrigin :: Annex Bool
hasOrigin = refExists originname

{- Does the git-annex branch or a foo/git-annex branch exist? -}
hasSomeBranch :: Annex Bool
hasSomeBranch = not . null <$> siblingBranches

{- List of git-annex (refs, branches), including the main one and any
 - from remotes. Duplicate refs are filtered out. -}
siblingBranches :: Annex [(Git.Ref, Git.Branch)]
siblingBranches = do
	r <- inRepo $ Git.pipeRead [Param "show-ref", Param $ show name]
	return $ nubBy uref $ map (gen . words . L.unpack) (L.lines r)
	where
		gen l = (Git.Ref $ head l, Git.Ref $ last l)
		uref (a, _) (b, _) = a == b

{- Get the ref of a branch. -}
getRef :: Git.Ref -> Annex (Maybe Git.Ref)
getRef branch = process . L.unpack <$> showref
	where
		showref = inRepo $ Git.pipeRead [Param "show-ref",
			Param "--hash", -- get the hash
			Params "--verify", -- only exact match
			Param $ show branch]
		process [] = Nothing
		process s = Just $ firstRef s

firstRef :: String-> Git.Ref
firstRef = Git.Ref . takeWhile (/= '\n')

{- Applies a function to modifiy the content of a file.
 -
 - Note that this does not cause the branch to be merged, it only
 - modifes the current content of the file on the branch.
 -}
change :: FilePath -> (String -> String) -> Annex ()
change file a = lockJournal $ getStale file >>= return . a >>= set file

{- Records new content of a file into the journal. -}
set :: FilePath -> String -> Annex ()
set file content = do
	setJournalFile file content
	setCache file content

{- Gets the content of a file on the branch, or content from the journal, or
 - staged in the index.
 -
 - Returns an empty string if the file doesn't exist yet. -}
get :: FilePath -> Annex String
get = get' False

{- Like get, but does not merge the branch, so the info returned may not
 - reflect changes in remotes. (Changing the value this returns, and then
 - merging is always the same as using get, and then changing its value.) -}
getStale :: FilePath -> Annex String
getStale = get' True

get' :: Bool -> FilePath -> Annex String
get' staleok file = fromcache =<< getCache file
	where
		fromcache (Just content) = return content
		fromcache Nothing = fromjournal =<< getJournalFile file
		fromjournal (Just content) = cache content
		fromjournal Nothing
			| staleok = withIndex frombranch
			| otherwise = withIndexUpdate $ frombranch >>= cache
		frombranch = L.unpack <$> catFile fullname file
		cache content = do
			setCache file content
			return content

{- Lists all files on the branch. There may be duplicates in the list. -}
files :: Annex [FilePath]
files = withIndexUpdate $ do
	bfiles <- inRepo $ Git.pipeNullSplit
		[Params "ls-tree --name-only -r -z", Param $ show fullname]
	jfiles <- getJournalledFiles
	return $ jfiles ++ bfiles

{- Records content for a file in the branch to the journal.
 -
 - Using the journal, rather than immediatly staging content to the index
 - avoids git needing to rewrite the index after every change. -}
setJournalFile :: FilePath -> String -> Annex ()
setJournalFile file content = do
	g <- gitRepo
	liftIO $ doRedo (write g) $ do
		createDirectoryIfMissing True $ gitAnnexJournalDir g
		createDirectoryIfMissing True $ gitAnnexTmpDir g
	where
		-- journal file is written atomically
		write g = do
			let jfile = journalFile g file
			let tmpfile = gitAnnexTmpDir g </> takeFileName jfile
			writeBinaryFile tmpfile content
			moveFile tmpfile jfile

{- Gets any journalled content for a file in the branch. -}
getJournalFile :: FilePath -> Annex (Maybe String)
getJournalFile file = inRepo $ \g -> catchMaybeIO $
	readFileStrict $ journalFile g file

{- List of files that have updated content in the journal. -}
getJournalledFiles :: Annex [FilePath]
getJournalledFiles = map fileJournal <$> getJournalFiles

{- List of existing journal files. -}
getJournalFiles :: Annex [FilePath]
getJournalFiles = do
	g <- gitRepo
	fs <- liftIO $
		catchDefaultIO (getDirectoryContents $ gitAnnexJournalDir g) []
	return $ filter (`notElem` [".", ".."]) fs

{- Stages the specified journalfiles. -}
stageJournalFiles :: Annex ()
stageJournalFiles = do
	fs <- getJournalFiles
	g <- gitRepo
	withIndex $ liftIO $ do
		let dir = gitAnnexJournalDir g
		let paths = map (dir </>) fs
		-- inject all the journal files directly into git
		-- in one quick command
		(pid, fromh, toh) <- hPipeBoth "git" $ toCommand $ git_hash_object g
		_ <- forkProcess $ do
			hPutStr toh $ unlines paths
			hClose toh
			exitSuccess
		hClose toh
		shas <- map Git.Ref . lines <$> hGetContents fromh
		-- update the index, also in just one command
		Git.UnionMerge.update_index g $
			index_lines shas (map fileJournal fs)
		hClose fromh
		forceSuccess pid
		mapM_ removeFile paths
	where
		index_lines shas = map genline . zip shas
		genline (sha, file) = Git.UnionMerge.update_index_line sha file
		git_hash_object = Git.gitCommandLine
			[Param "hash-object", Param "-w", Param "--stdin-paths"]


{- Checks if there are changes in the journal. -}
journalDirty :: Annex Bool
journalDirty = not . null <$> getJournalFiles

{- Produces a filename to use in the journal for a file on the branch.
 -
 - The journal typically won't have a lot of files in it, so the hashing
 - used in the branch is not necessary, and all the files are put directly
 - in the journal directory.
 -}
journalFile :: Git.Repo -> FilePath -> FilePath
journalFile repo file = gitAnnexJournalDir repo </> concatMap mangle file
	where
		mangle '/' = "_"
		mangle '_' = "__"
		mangle c = [c]

{- Converts a journal file (relative to the journal dir) back to the
 - filename on the branch. -}
fileJournal :: FilePath -> FilePath
fileJournal = replace "//" "_" . replace "_" "/"

{- Runs an action that modifies the journal, using locking to avoid
 - contention with other git-annex processes. -}
lockJournal :: Annex a -> Annex a
lockJournal a = do
	file <- fromRepo gitAnnexJournalLock
	bracketIO (lock file) unlock a
	where
		lock file = do
			l <- doRedo (createFile file stdFileMode) $
				createDirectoryIfMissing True $ takeDirectory file
			waitToSetLock l (WriteLock, AbsoluteSeek, 0, 0)
			return l
		unlock = closeFd

{- Runs an action, catching failure and running something to fix it up, and
 - retrying if necessary. -}
doRedo :: IO a -> IO b -> IO a
doRedo a b = catch a $ const $ b >> a