Now gitattributes are looked up, efficiently, in only the places that
really need them, using the same approach used for cat-file.
The old CheckAttr code seemed very fragile, in the way it streamed files
through git check-attr.
I actually found that cad8824852
was still deadlocking with ghc 7.4, at the end of adding a lot of files.
This should fix that problem, and avoid future ones.
The best part is that this removes withAttrFilesInGit and withNumCopies,
which were complicated Seek methods, as well as simplfying the types
for several other Seek methods that had a Backend tupled in.
Under ghc 7.4, this seems to be able to handle all filename encodings
again. Including filename encodings that do not match the LANG setting.
I think this will not work with earlier versions of ghc, it uses some ghc
internals.
Turns out that ghc 7.4 has a special filesystem encoding that it uses when
reading/writing filenames (as FilePaths). This encoding is documented
to allow "arbitrary undecodable bytes to be round-tripped through it".
So, to get FilePaths from eg, git ls-files, set the Handle that is reading
from git to use this encoding. Then things basically just work.
However, I have not found a way to make Text read using this encoding.
Text really does assume unicode. So I had to switch back to using String
when reading/writing data to git. Which is a pity, because it's some
percent slower, but at least it works.
Note that stdout and stderr also have to be set to this encoding, or
printing out filenames that contain undecodable bytes causes a crash.
IMHO this is a misfeature in ghc, that the user can pass you a filename,
which you can readFile, etc, but that default, putStr of filename may
cause a crash!
Git.CheckAttr gave me special trouble, because the filenames I got back
from git, after feeding them in, had further encoding breakage.
Rather than try to deal with that, I just zip up the input filenames
with the attributes. Which must be returned in the same order queried
for this to work.
Also of note is an apparent GHC bug I worked around in Git.CheckAttr. It
used to forkProcess and feed git from the child process. Unfortunatly,
after this forkProcess, accessing the `files` variable from the parent
returns []. Not the value that was passed into the function. This screams
of a bad bug, that's clobbering a variable, but for now I just avoid
forkProcess there to work around it. That forkProcess was itself only added
because of a ghc bug, #624389. I've confirmed that the test case for that
bug doesn't reproduce it with ghc 7.4. So that's ok, except for the new ghc
bug I have not isolated and reported. Why does this simple bit of code
magnet the ghc bugs? :)
Also, the symlink touching code is currently broken, when used on utf-8
filenames in a non-utf-8 locale, or probably on any filename containing
undecodable bytes, and I temporarily commented it out.
I had not realized what a memory leak the lazy state monad could be,
although I have not seen much evidence of actual leaking in git-annex.
However, if running git-annex on a great many files, this could matter.
The additional Utility.State.changeState adds even more strictness,
avoiding a problem I saw in github-backup where repeatedly modifying
state built up a huge pile of thunks.
This drops the >>! and >>? with the nice low fixity. IfElse does have
undocumented >>=>>! and >>=>>? operators, but I deem that too fishy.
Anyway, using whenM and unlessM is easier; I sometimes mixed the operators
up.
This overrides the trust.log, and is overridden by the command-line trust
parameters.
It would have been nicer to have Logs.Trust.trustMap just look up the
configuration for all remotes, but a dependency loop prevented that
(Remotes depends on Logs.Trust in several ways). So instead, look up
the configuration when building remotes, storing it in the same forcetrust
field used for the command-line trust parameters.
Turns out that git will accept a .git/config containing an url with eg,
spaces in its name. Handle this by escaping the url if it's not valid.
This also fixes support for urls containing escaped characters like %20
for space. Before, the path from the url was not unescaped properly.
With --fast, unavailable local remotes are filtered out of the fast set.
This way, if there are local remotes, --fast always acts only on them,
and if none are mounted, acts on nothing. This consistency is better
than --fast acting on different remotes depending on what's mounted.
The describe function was only intended to generate a human-visible
description of a branch, but taking the base of a branch is a useful
operation to be able to do no matter the human-visible representation.
Converting a branch like refs/heads/master to refs/heads/origin/master
is also a useful operation, and under can do that.
Consider this git config --list case:
url.git+ssh://git@example.com/.insteadOf=gl
url.git+ssh://git@example.com/.insteadOf=shared
Since config is stored in a Map, only the last of the values for this key
was stored and available for use by the insteadOf code. But that
is wrong; git allows either "gl" or "shared" to be used in an url and
the insteadOf value to be substituted in.
To support this, it seems best to keep the existing config map as-is,
and add a second map that accumulates a list of multiple values for
config keys. This new fullconfig map can be used in the rare places where
multiple values for a key make sense, without needing to complicate
everything else.
Haskell's laziness and data sharing keep the overhead of adding
this second map low.
I was happily able to repurpose some code from Git.Filename to handle this.
I remember writing that code... a whole afternoon at a coffee shop, after
which I felt I'd struggled with Haskell and git, and sorta lost, in needing
to write this nasty peice of code. But was also pleased at the use of a
pair of functions and quickcheck that allowed me to get it 100% right.
So, turns out I not only got it right, but the code wasn't as special-purpose
as I'd feared. Yay!
A crash on parsing was fixed a while ago. This adds support for fully
correctly parsing multiline git config values, using git config --null.
Since git-annex-shell configlist uses normal git config output, I left in
support for that too; the two forms of config output can be easily
identified by the parser. Since configlist only prints the annex.uuid
config, there's no risk of multiline values there, so no need to change it.
Could have just used hGetContentsStrict here, but that would require
storing all the shas in memory. Since this is called at the end of a
git-annex run, it may have created a *lot* of shas, so I avoid that memory
use and stream them out like before.
Testing b9ac585454, it didn't find the
optimal union merge, the second sha was the one to use, at least in
the case I tried. Let's just try all shas to see if any can be reused.
I stopped using the expensive nub, so despite the use of sets to
sort/uniq file contents, this is probably as fast or faster than it
was before.
Tries to avoid generating a new object when the merged content has the same
lines that were in the old object.
I've noticed some merge commits that only move lines around, like this:
- 1323478057.181191s 1 be23c3ac-0ee5-11e0-b185-3b0f9b5b00c5
1323204972.062151s 1 87e06c7a-7388-11e0-ba07-03cdf300bd87
++1323478057.181191s 1 be23c3ac-0ee5-11e0-b185-3b0f9b5b00c5
Unsure if this will really save anything in practice, since it only looks
at one of the two old objects, and maybe I didn't pick the best one.
In git, a Ref can be a Sha, or a Branch, or a Tag. I added type aliases for
those. Note that this does not prevent mixing up of eg, refs and branches
at the type level. Since git really doesn't care, except rare cases like
git update-ref, or git tag -d, that seems ok for now.
There's also a tree-ish, but let's just use Ref for it. A given Sha or Ref
may or may not be a tree-ish, depending on the object type, so there seems
no point in trying to represent it at the type level.
Before, a merge was first calculated, by running various actions that
called git and built up a list of lines, which were at the end sent
to git update-index. This necessarily used space proportional to the size
of the diff between the trees being merged.
Now, lines are streamed into git update-index from each of the actions in
turn.
Runtime size of git-annex merge when merging 50000 location log files
drops from around 100 mb to a constant 4 mb.
Presumably it runs quite a lot faster, too.
This reduces the memory use of a merge by 1/3rd. The space leak was
apparently because the whole update-index input was generated strictly, not
lazily.
I wondered if the change to ByteStrings contributed to this, due to the
need to convert with L.pack here. But going back to the old code, I still
see a much similar leak, and worse performance besides due to it not using
ByteStrings.
The fix is to just hPutStr the lines repeatedly. (Note the \0 is written
separately, to avoid allocation overheads in adding it to the string.)
The Git.pipeWrite interface is probably just wrong for any large inputs to
git. This was the only place using it for input of any size.
There is still at least one other space leak in the merge code.
Many functions took the repo as their first parameter. Changing it
consistently to be the last parameter allows doing some useful things with
currying, that reduce boilerplate.
In particular, g <- gitRepo is almost never needed now, instead
use inRepo to run an IO action in the repo, and fromRepo to get
a value from the repo.
This also provides more opportunities to use monadic and applicative
combinators.
This yields a second or so speedup in unused, find, etc. Seems that even
when the ByteString is immediately split and then converted to Strings,
it's faster.
I may try to push ByteStrings out into more of git-annex gradually,
although I suspect most of the time-critical parts are already covered
now, and many of the rest rely on libraries that only support Strings.
Added Git.ByteString which replaces Git IO methods with ones using lazy
ByteStrings. This can be more efficient when large quantities of data are
being read from git.
In Git.LsTree, parse git ls-tree output more efficiently, thanks
to ByteString. This benchmarks 25% faster, in a benchmark that includes
(probably predominately) the run time for git ls-tree itself.
In real world numbers, this makes git annex unused 2 seconds faster for
each branch it needs to check, in my usual large repo.
This was more complex than would be expected. unannex has to use git commit -a
since it's removing files from git; git commit filelist won't do.
Allow commands to be added to the Git queue that have no associated files,
and run such commands once.
