This changes the behavior of callbacks so that the callback error code is not converted into GIT_EUSER and instead we propagate the return value through to the caller. Instead of using the giterr_capture and giterr_restore functions, we now rely on all functions to pass back the return value from a callback. To avoid having a return value with no error message, the user can call the public giterr_set_str or some such function to set an error message. There is a new helper 'giterr_set_callback' that functions can invoke after making a callback which ensures that some error message was set in case the callback did not set one. In places where the sign of the callback return value is meaningful (e.g. positive to skip, negative to abort), only the negative values are returned back to the caller, obviously, since the other values allow for continuing the loop. The hardest parts of this were in the checkout code where positive return values were overloaded as meaningful values for checkout. I fixed this by adding an output parameter to many of the internal checkout functions and removing the overload. This added some code, but it is probably a better implementation. There is some funkiness in the network code where user provided callbacks could be returning a positive or a negative value and we want to rely on that to cancel the loop. There are still a couple places where an user error might get turned into GIT_EUSER there, I think, though none exercised by the tests.
This adds giterr_user_cancel to return GIT_EUSER and clear any error message that is sitting around. As a result of using that in places, we need to be more thorough with capturing errors that happen inside a callback when used internally. To help with that, this also adds giterr_capture and giterr_restore so that when we internally use a foreach-type function that clears errors and converts them to GIT_EUSER, it is easier to restore not just the return value, but the actual error message text.
It was there to keep it apart from the one which read in from a file on disk. This other indexer does not exist anymore, so there is no need for anything other than git_indexer to refer to it. While here, rename _add() function to _append() and _finalize() to _commit(). The former change is cosmetic, while the latter avoids talking about "finalizing", which OO languages use to mean something completely different.
Add support for thin packs
When given an ODB from which to read objects, the indexer will attempt to inject the missing bases at the end of the pack and update the header and trailer to reflect the new contents.
This hooks up git_path_direach and git_path_dirload so that they will take a flag indicating if directory entry names should be tested and converted from decomposed unicode to precomposed form. This code will only come into play on the Apple platform and even then, only when certain types of filesystems are used. This involved adding a flag to these functions which involved changing a lot of places in the code. This was an opportunity to do a bit of code cleanup here and there, for example, getting rid of the git_futils_cleanupdir_r function in favor of a simple flag to git_futils_rmdir_r to not remove the top level entry. That ended up adding depth tracking during rmdir_r which led to a safety check for infinite directory recursion. Yay. This hasn't actually been tested on the Mac filesystems where the issue occurs. I still need to get test environment for that.