Make Utility.Process wrap the parts of System.Process that I use,
and add debug logging to them.
Also wrote some higher-level code that allows running an action
with handles to a processes stdin or stdout (or both), and checking
its exit status, all in a single function call.
As a bonus, the debug logging now indicates whether the process
is being run to read from it, feed it data, chat with it (writing and
reading), or just call it for its side effect.
Test suite now passes with -threaded!
I traced back all the hangs with -threaded to System.Cmd.Utils. It seems
it's just crappy/unsafe/outdated, and should not be used. System.Process
seems to be the cool new thing, so converted all the code to use it
instead.
In the process, --debug stopped printing commands it runs. I may try to
bring that back later.
Note that even SafeSystem was switched to use System.Process. Since that
was a modified version of code from System.Cmd.Utils, it needed to be
converted too. I also got rid of nearly all calls to forkProcess,
and all calls to executeFile, which I'm also doubtful about working
well with -threaded.
While I was in there, I noticed and fixed a bug in the queue size
calculations. It was never encountered only because Queue.add was
only ever run with 1 file in the list.
This allows the queue to be used in a single process for multiple possibly
conflicting commands, like add and rm, without running them out of order.
This assumes that running the same git subcommand with different parameters
cannot itself conflict.
useful when adding hundreds of thousands of files on a system with plenty
of memory.
git add gets quite slow in such a large repository, so if the system has
more than the ~32 mb of memory the queue can use by default, it's a useful
optimisation to increase the queue size, in order to decrease the number
of times git add is run.
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.
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 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.
