summaryrefslogtreecommitdiff
path: root/Annex/Content.hs
blob: b51e15827b58b5653c2892c88a9e5d1f44e8b4eb (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
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
{- git-annex file content managing
 -
 - Copyright 2010-2014 Joey Hess <joey@kitenet.net>
 -
 - Licensed under the GNU GPL version 3 or higher.
 -}

{-# LANGUAGE CPP #-}

module Annex.Content (
	inAnnex,
	inAnnexSafe,
	inAnnexCheck,
	lockContent,
	getViaTmp,
	getViaTmpChecked,
	getViaTmpUnchecked,
	prepGetViaTmpChecked,
	prepTmp,
	withTmp,
	checkDiskSpace,
	moveAnnex,
	sendAnnex,
	prepSendAnnex,
	removeAnnex,
	fromAnnex,
	moveBad,
	KeyLocation(..),
	getKeysPresent,
	saveState,
	downloadUrl,
	preseedTmp,
	freezeContent,
	thawContent,
	dirKeys,
	withObjectLoc,
) where

import System.IO.Unsafe (unsafeInterleaveIO)

import Common.Annex
import Logs.Location
import qualified Git
import qualified Annex
import qualified Annex.Queue
import qualified Annex.Branch
import Utility.DiskFree
import Utility.FileMode
import qualified Annex.Url as Url
import Types.Key
import Utility.DataUnits
import Utility.CopyFile
import Config
import Git.SharedRepository
import Annex.Perms
import Annex.Link
import Annex.Content.Direct
import Annex.ReplaceFile

#ifdef mingw32_HOST_OS
import Utility.WinLock
#endif

{- Checks if a given key's content is currently present. -}
inAnnex :: Key -> Annex Bool
inAnnex key = inAnnexCheck key $ liftIO . doesFileExist

{- Runs an arbitrary check on a key's content. -}
inAnnexCheck :: Key -> (FilePath -> Annex Bool) -> Annex Bool
inAnnexCheck key check = inAnnex' id False check key

{- Generic inAnnex, handling both indirect and direct mode.
 -
 - In direct mode, at least one of the associated files must pass the
 - check. Additionally, the file must be unmodified.
 -}
inAnnex' :: (a -> Bool) -> a -> (FilePath -> Annex a) -> Key -> Annex a
inAnnex' isgood bad check key = withObjectLoc key checkindirect checkdirect
  where
	checkindirect loc = do
		whenM (fromRepo Git.repoIsUrl) $
			error "inAnnex cannot check remote repo"
		check loc
	checkdirect [] = return bad
	checkdirect (loc:locs) = do
		r <- check loc
		if isgood r
			then ifM (goodContent key loc)
				( return r
				, checkdirect locs
				)
			else checkdirect locs

{- A safer check; the key's content must not only be present, but
 - is not in the process of being removed. -}
inAnnexSafe :: Key -> Annex (Maybe Bool)
inAnnexSafe key = inAnnex' (fromMaybe False) (Just False) go key
  where
	is_locked = Nothing
	is_unlocked = Just True
	is_missing = Just False

	go contentfile = maybe (checkindirect contentfile) (checkdirect contentfile)
		=<< contentLockFile key

#ifndef mingw32_HOST_OS
	checkindirect f = liftIO $ openforlock f >>= check is_missing
	{- In direct mode, the content file must exist, but
	 - the lock file often generally won't exist unless a removal is in
	 - process. This does not create the lock file, it only checks for
	 - it. -}
	checkdirect contentfile lockfile = liftIO $
		ifM (doesFileExist contentfile)
			( openforlock lockfile >>= check is_unlocked
			, return is_missing
			)
	openforlock f = catchMaybeIO $
		openFd f ReadOnly Nothing defaultFileFlags
	check _ (Just h) = do
		v <- getLock h (ReadLock, AbsoluteSeek, 0, 0)
		closeFd h
		return $ case v of
			Just _ -> is_locked
			Nothing -> is_unlocked
	check def Nothing = return def
#else
	checkindirect f = liftIO $ ifM (doesFileExist f)
		( do
			v <- lockShared f
			case v of
				Nothing -> return is_locked
				Just lockhandle -> do
					dropLock lockhandle
					return is_unlocked
		, return is_missing
		)
	{- In Windows, see if we can take a shared lock. If so, 
	 - remove the lock file to clean up after ourselves. -}
	checkdirect contentfile lockfile =
		ifM (liftIO $ doesFileExist contentfile)
			( modifyContent lockfile $ liftIO $ do
				v <- lockShared lockfile
				case v of
					Nothing -> return is_locked
					Just lockhandle -> do
						dropLock lockhandle
						void $ tryIO $ nukeFile lockfile
						return is_unlocked
			, return is_missing
			)
#endif

{- Direct mode and especially Windows has to use a separate lock
 - file from the content, since locking the actual content file
 - would interfere with the user's use of it. -}
contentLockFile :: Key -> Annex (Maybe FilePath)
contentLockFile key = ifM isDirect
	( Just <$> calcRepo (gitAnnexContentLock key)
	, return Nothing
	)

{- Content is exclusively locked while running an action that might remove
 - it. (If the content is not present, no locking is done.) -}
lockContent :: Key -> Annex a -> Annex a
lockContent key a = do
	contentfile <- calcRepo $ gitAnnexLocation key
	lockfile <- contentLockFile key
	maybe noop setuplockfile lockfile
	bracket (liftIO $ lock contentfile lockfile) (unlock lockfile) (const a)
  where
	alreadylocked = error "content is locked"
	setuplockfile lockfile = modifyContent lockfile $
		void $ liftIO $ tryIO $
			writeFile lockfile ""
	cleanuplockfile lockfile = modifyContent lockfile $
		void $ liftIO $ tryIO $
			nukeFile lockfile
#ifndef mingw32_HOST_OS
	lock contentfile Nothing = opencontentforlock contentfile >>= dolock
	lock _ (Just lockfile) = openforlock lockfile >>= dolock . Just
	{- Since content files are stored with the write bit disabled, have
	 - to fiddle with permissions to open for an exclusive lock. -}
	opencontentforlock f = catchMaybeIO $ ifM (doesFileExist f)
		( withModifiedFileMode f
			(`unionFileModes` ownerWriteMode)
			(openforlock f)
		, openforlock f
		)
	openforlock f = openFd f ReadWrite Nothing defaultFileFlags
	dolock Nothing = return Nothing
	dolock (Just fd) = do
		v <- tryIO $ setLock fd (WriteLock, AbsoluteSeek, 0, 0)
		case v of
			Left _ -> alreadylocked
			Right _ -> return $ Just fd
	unlock mlockfile mfd = do
		maybe noop cleanuplockfile mlockfile
		liftIO $ maybe noop closeFd mfd
#else
	lock _ (Just lockfile) = maybe alreadylocked (return . Just) =<< lockExclusive lockfile
	lock _ Nothing = return Nothing
	unlock mlockfile mlockhandle = do
		liftIO $ maybe noop dropLock mlockhandle
		maybe noop cleanuplockfile mlockfile
#endif

{- Runs an action, passing it a temporary filename to get,
 - and if the action succeeds, moves the temp file into 
 - the annex as a key's content. -}
getViaTmp :: Key -> (FilePath -> Annex Bool) -> Annex Bool
getViaTmp = getViaTmpChecked (return True)

{- Like getViaTmp, but does not check that there is enough disk space
 - for the incoming key. For use when the key content is already on disk
 - and not being copied into place. -}
getViaTmpUnchecked :: Key -> (FilePath -> Annex Bool) -> Annex Bool
getViaTmpUnchecked = finishGetViaTmp (return True)

getViaTmpChecked :: Annex Bool -> Key -> (FilePath -> Annex Bool) -> Annex Bool
getViaTmpChecked check key action = 
	prepGetViaTmpChecked key False $
		finishGetViaTmp check key action

{- Prepares to download a key via a tmp file, and checks that there is
 - enough free disk space.
 -
 - When the temp file already exists, count the space it is using as
 - free, since the download will overwrite it or resume.
 -
 - Wen there's enough free space, runs the download action.
 -}
prepGetViaTmpChecked :: Key -> a -> Annex a -> Annex a
prepGetViaTmpChecked key unabletoget getkey = do
	tmp <- fromRepo $ gitAnnexTmpObjectLocation key

	e <- liftIO $ doesFileExist tmp
	alreadythere <- if e
		then fromIntegral . fileSize <$> liftIO (getFileStatus tmp)
		else return 0
	ifM (checkDiskSpace Nothing key alreadythere)
		( do
			-- The tmp file may not have been left writable
			when e $ thawContent tmp
			getkey
		, return unabletoget
		)

finishGetViaTmp :: Annex Bool -> Key -> (FilePath -> Annex Bool) -> Annex Bool
finishGetViaTmp check key action = do
	tmpfile <- prepTmp key
	ifM (action tmpfile <&&> check)
		( do
			moveAnnex key tmpfile
			logStatus key InfoPresent
			return True
		-- the tmp file is left behind, in case caller wants
		-- to resume its transfer
		, return False
		)

prepTmp :: Key -> Annex FilePath
prepTmp key = do
	tmp <- fromRepo $ gitAnnexTmpObjectLocation key
	createAnnexDirectory (parentDir tmp)
	return tmp

{- Creates a temp file for a key, runs an action on it, and cleans up
 - the temp file. If the action throws an exception, the temp file is
 - left behind, which allows for resuming.
 -}
withTmp :: Key -> (FilePath -> Annex a) -> Annex a
withTmp key action = do
	tmp <- prepTmp key
	res <- action tmp
	liftIO $ nukeFile tmp
	return res

{- Checks that there is disk space available to store a given key,
 - in a destination (or the annex) printing a warning if not. -}
checkDiskSpace :: Maybe FilePath -> Key -> Integer -> Annex Bool
checkDiskSpace destination key alreadythere = do
	reserve <- annexDiskReserve <$> Annex.getGitConfig
	free <- liftIO . getDiskFree =<< dir
	force <- Annex.getState Annex.force
	case (free, keySize key) of
		(Just have, Just need) -> do
			let ok = (need + reserve <= have + alreadythere) || force
			unless ok $
				needmorespace (need + reserve - have - alreadythere)
			return ok
		_ -> return True
  where
	dir = maybe (fromRepo gitAnnexDir) return destination
	needmorespace n =
		warning $ "not enough free space, need " ++ 
			roughSize storageUnits True n ++
			" more" ++ forcemsg
	forcemsg = " (use --force to override this check or adjust annex.diskreserve)"

{- Moves a key's content into .git/annex/objects/
 -
 - In direct mode, moves it to the associated file, or files.
 -
 - What if the key there already has content? This could happen for
 - various reasons; perhaps the same content is being annexed again.
 - Perhaps there has been a hash collision generating the keys.
 -
 - The current strategy is to assume that in this case it's safe to delete
 - one of the two copies of the content; and the one already in the annex
 - is left there, assuming it's the original, canonical copy.
 -
 - I considered being more paranoid, and checking that both files had
 - the same content. Decided against it because A) users explicitly choose
 - a backend based on its hashing properties and so if they're dealing
 - with colliding files it's their own fault and B) adding such a check
 - would not catch all cases of colliding keys. For example, perhaps 
 - a remote has a key; if it's then added again with different content then
 - the overall system now has two different peices of content for that
 - key, and one of them will probably get deleted later. So, adding the
 - check here would only raise expectations that git-annex cannot truely
 - meet.
 -}
moveAnnex :: Key -> FilePath -> Annex ()
moveAnnex key src = withObjectLoc key storeobject storedirect
  where
	storeobject dest = ifM (liftIO $ doesFileExist dest)
		( alreadyhave
		, modifyContent dest $ do
			liftIO $ moveFile src dest
			freezeContent dest
		)
	storeindirect = storeobject =<< calcRepo (gitAnnexLocation key)

	{- In direct mode, the associated file's content may be locally
	 - modified. In that case, it's preserved. However, the content
	 - we're moving into the annex may be the only extant copy, so
	 - it's important we not lose it. So, when the key's content
	 - cannot be moved to any associated file, it's stored in indirect
	 - mode.
	 -}
	storedirect = storedirect' storeindirect
	storedirect' fallback [] = fallback
	storedirect' fallback (f:fs) = do
		thawContent src
		v <- isAnnexLink f
		if Just key == v
			then do
				updateInodeCache key src
				replaceFile f $ liftIO . moveFile src
				chmodContent f
				forM_ fs $
					addContentWhenNotPresent key f
			else ifM (goodContent key f)
				( storedirect' alreadyhave fs
				, storedirect' fallback fs
				)
	
	alreadyhave = liftIO $ removeFile src

{- Runs an action to transfer an object's content.
 -
 - In direct mode, it's possible for the file to change as it's being sent.
 - If this happens, runs the rollback action and returns False. The
 - rollback action should remove the data that was transferred.
 -}
sendAnnex :: Key -> Annex () -> (FilePath -> Annex Bool) -> Annex Bool
sendAnnex key rollback sendobject = go =<< prepSendAnnex key
  where
	go Nothing = return False
	go (Just (f, checksuccess)) = do
		r <- sendobject f
		ifM checksuccess
			( return r
			, do
				rollback
				return False
			)

{- Returns a file that contains an object's content,
 - and an check to run after the transfer is complete.
 -
 - In direct mode, it's possible for the file to change as it's being sent,
 - and the check detects this case and returns False.
 -
 - Note that the returned check action is, in some cases, run in the
 - Annex monad of the remote that is receiving the object, rather than
 - the sender. So it cannot rely on Annex state.
 -}
prepSendAnnex :: Key -> Annex (Maybe (FilePath, Annex Bool))
prepSendAnnex key = withObjectLoc key indirect direct
  where
	indirect f = return $ Just (f, return True)
	direct [] = return Nothing
	direct (f:fs) = do
		cache <- recordedInodeCache key
		-- check that we have a good file
		ifM (sameInodeCache f cache)
			( return $ Just (f, sameInodeCache f cache)
			, direct fs
			)

{- Performs an action, passing it the location to use for a key's content.
 -
 - In direct mode, the associated files will be passed. But, if there are
 - no associated files for a key, the indirect mode action will be
 - performed instead. -}
withObjectLoc :: Key -> (FilePath -> Annex a) -> ([FilePath] -> Annex a) -> Annex a
withObjectLoc key indirect direct = ifM isDirect
	( do
		fs <- associatedFiles key
		if null fs
			then goindirect
			else direct fs
	, goindirect
	)
  where
	goindirect = indirect =<< calcRepo (gitAnnexLocation key)

cleanObjectLoc :: Key -> Annex () -> Annex ()
cleanObjectLoc key cleaner = do
	file <- calcRepo $ gitAnnexLocation key
	void $ tryIO $ thawContentDir file
	cleaner
	liftIO $ removeparents file (3 :: Int)
  where
	removeparents _ 0 = noop
	removeparents file n = do
		let dir = parentDir file
		maybe noop (const $ removeparents dir (n-1))
			<=< catchMaybeIO $ removeDirectory dir

{- Removes a key's file from .git/annex/objects/
 -
 - In direct mode, deletes the associated files or files, and replaces
 - them with symlinks. -}
removeAnnex :: Key -> Annex ()
removeAnnex key = withObjectLoc key remove removedirect
  where
	remove file = cleanObjectLoc key $ do
		secureErase file
		liftIO $ nukeFile file
		removeInodeCache key
	removedirect fs = do
		cache <- recordedInodeCache key
		removeInodeCache key
		mapM_ (resetfile cache) fs
	resetfile cache f = whenM (sameInodeCache f cache) $ do
		l <- inRepo $ gitAnnexLink f key
		secureErase f
		replaceFile f $ makeAnnexLink l

{- Runs the secure erase command if set, otherwise does nothing.
 - File may or may not be deleted at the end; caller is responsible for
 - making sure it's deleted. -}
secureErase :: FilePath -> Annex ()
secureErase file = maybe noop go =<< annexSecureEraseCommand <$> Annex.getGitConfig
  where
  	go basecmd = void $ liftIO $
		boolSystem "sh" [Param "-c", Param $ gencmd basecmd]
	gencmd = massReplace [ ("%file", shellEscape file) ]

{- Moves a key's file out of .git/annex/objects/ -}
fromAnnex :: Key -> FilePath -> Annex ()
fromAnnex key dest = cleanObjectLoc key $ do
	file <- calcRepo $ gitAnnexLocation key
	thawContent file
	liftIO $ moveFile file dest

{- Moves a key out of .git/annex/objects/ into .git/annex/bad, and
 - returns the file it was moved to. -}
moveBad :: Key -> Annex FilePath
moveBad key = do
	src <- calcRepo $ gitAnnexLocation key
	bad <- fromRepo gitAnnexBadDir
	let dest = bad </> takeFileName src
	createAnnexDirectory (parentDir dest)
	cleanObjectLoc key $
		liftIO $ moveFile src dest
	logStatus key InfoMissing
	return dest

data KeyLocation = InAnnex | InRepository

{- List of keys whose content exists in the specified location.
 
 - InAnnex only lists keys under .git/annex/objects,
 - while InRepository, in direct mode, also finds keys located in the
 - work tree.
 -
 - Note that InRepository has to check whether direct mode files
 - have goodContent.
 -}
getKeysPresent :: KeyLocation -> Annex [Key]
getKeysPresent keyloc = do
	direct <- isDirect
	dir <- fromRepo gitAnnexObjectDir
	s <- getstate direct
	liftIO $ traverse s direct (2 :: Int) dir
  where
	traverse s direct depth dir = do
		contents <- catchDefaultIO [] (dirContents dir)
		if depth == 0
			then do
				contents' <- filterM (present s direct) contents
				let keys = mapMaybe (fileKey . takeFileName) contents'
				continue keys []
			else do
				let deeper = traverse s direct (depth - 1)
				continue [] (map deeper contents)
	continue keys [] = return keys
	continue keys (a:as) = do
		{- Force lazy traversal with unsafeInterleaveIO. -}
		morekeys <- unsafeInterleaveIO a
		continue (morekeys++keys) as

	present _ False d = presentInAnnex d
	present s True d = presentDirect s d <||> presentInAnnex d

	presentInAnnex = doesFileExist . contentfile
	contentfile d = d </> takeFileName d

	presentDirect s d = case keyloc of
		InAnnex -> return False
		InRepository -> case fileKey (takeFileName d) of
			Nothing -> return False
			Just k -> Annex.eval s $ 
				anyM (goodContent k) =<< associatedFiles k

	{- In order to run Annex monad actions within unsafeInterleaveIO,
	 - the current state is taken and reused. No changes made to this
	 - state will be preserved. 
	 -
	 - As an optimsation, call inodesChanged to prime the state with
	 - a cached value that will be used in the call to goodContent.
	 -}
	getstate direct = do
		when direct $
			void $ inodesChanged
		Annex.getState id

{- Things to do to record changes to content when shutting down.
 -
 - It's acceptable to avoid committing changes to the branch,
 - especially if performing a short-lived action.
 -}
saveState :: Bool -> Annex ()
saveState nocommit = doSideAction $ do
	Annex.Queue.flush
	unless nocommit $
		whenM (annexAlwaysCommit <$> Annex.getGitConfig) $
			Annex.Branch.commit "update"

{- Downloads content from any of a list of urls. -}
downloadUrl :: [Url.URLString] -> FilePath -> Annex Bool
downloadUrl urls file = go =<< annexWebDownloadCommand <$> Annex.getGitConfig
  where
  	go Nothing = Url.withUrlOptions $ \uo ->
		anyM (\u -> Url.download u file uo) urls
	go (Just basecmd) = liftIO $ anyM (downloadcmd basecmd) urls
	downloadcmd basecmd url =
		boolSystem "sh" [Param "-c", Param $ gencmd url basecmd]
			<&&> doesFileExist file
	gencmd url = massReplace
		[ ("%file", shellEscape file)
		, ("%url", shellEscape url)
		]

{- Copies a key's content, when present, to a temp file.
 - This is used to speed up some rsyncs. -}
preseedTmp :: Key -> FilePath -> Annex Bool
preseedTmp key file = go =<< inAnnex key
  where
	go False = return False
	go True = do
		ok <- copy
		when ok $ thawContent file
		return ok
	copy = ifM (liftIO $ doesFileExist file)
		( return True
		, do
			s <- calcRepo $ gitAnnexLocation key
			liftIO $ copyFileExternal s file
		)

{- Blocks writing to an annexed file, and modifies file permissions to
 - allow reading it, per core.sharedRepository setting. -}
freezeContent :: FilePath -> Annex ()
freezeContent file = unlessM crippledFileSystem $
	liftIO . go =<< fromRepo getSharedRepository
  where
	go GroupShared = modifyFileMode file $
		removeModes writeModes .
		addModes [ownerReadMode, groupReadMode]
	go AllShared = modifyFileMode file $
		removeModes writeModes .
		addModes readModes
	go _ = modifyFileMode file $
		removeModes writeModes .
		addModes [ownerReadMode]

{- Adjusts read mode of annexed file per core.sharedRepository setting. -}
chmodContent :: FilePath -> Annex ()
chmodContent file = unlessM crippledFileSystem $
	liftIO . go =<< fromRepo getSharedRepository
  where
	go GroupShared = modifyFileMode file $
		addModes [ownerReadMode, groupReadMode]
	go AllShared = modifyFileMode file $
		addModes readModes
	go _ = modifyFileMode file $
		addModes [ownerReadMode]

{- Allows writing to an annexed file that freezeContent was called on
 - before. -}
thawContent :: FilePath -> Annex ()
thawContent file = unlessM crippledFileSystem $
	liftIO . go =<< fromRepo getSharedRepository
  where
	go GroupShared = groupWriteRead file
	go AllShared = groupWriteRead file
	go _ = allowWrite file

{- Finds files directly inside a directory like gitAnnexBadDir 
 - (not in subdirectories) and returns the corresponding keys. -}
dirKeys :: (Git.Repo -> FilePath) -> Annex [Key]
dirKeys dirspec = do
	dir <- fromRepo dirspec
	ifM (liftIO $ doesDirectoryExist dir)
		( do
			contents <- liftIO $ getDirectoryContents dir
			files <- liftIO $ filterM doesFileExist $
				map (dir </>) contents
			return $ mapMaybe (fileKey . takeFileName) files
		, return []
		)