We've accumulated quite some functions which are never used outside of their respective code unit, but which are lacking the `static` keyword. Add it to reduce their linkage scope and allow the compiler to optimize better.
Propagate failures caused by pool initialization errors.
libgit2 does not use `type_t` suffixes as it's redundant; thus, rename `git_iterator_type_t` to `git_iterator_t` for consistency.
Instead of using a signed type (`off_t`) use a new `git_object_size_t` for the sizes of objects.
When preparing options for the two iterators that are about to be diffed, we allocate a common prefix for both iterators depending on the options passed by the user. We do not check whether the allocation was successful, though. In fact, this isn't much of a problem, as using a `NULL` prefix is perfectly fine. But in the end, we probably want to detect that the system doesn't have any memory left, as we're unlikely to be able to continue afterwards anyway. While the issue is being fixed in the newly created function `diff_prepare_iterator_opts`, it has been previously existing in the previous macro `DIFF_FROM_ITERATORS` already.
While the `DIFF_FROM_ITERATORS` does make it shorter to implement the various `git_diff_foo_to_bar` functions, it is a complex and unreadable beast that implicitly assumes certain local variable names. This is not something desirable to have at all and obstructs understanding and more importantly debugging the code by quite a bit. The `DIFF_FROM_ITERATORS` macro basically removed the burden of having to derive the options for both iterators from a pair of iterator flags and the diff options. This patch introduces a new function that does the that exact and refactors all callers to manage the iterators by themselves. As we potentially need to allocate a shared prefix for the iterator, we need to tell the caller to allocate that prefix as soon as the options aren't required anymore. Thus, the function has a `char **prefix` out pointer that will get set to the allocated string and subsequently be free'd by the caller. While this patch increases the line count, I personally deem this to an acceptable tradeoff for increased readbiblity.
Our file utils functions all have a "futils" prefix, e.g. `git_futils_touch`. One would thus naturally guess that their definitions and implementation would live in files "futils.h" and "futils.c", respectively, but in fact they live in "fileops.h". Rename the files to match expectations.
`cvar` is an unhelpful name. Refactor its usage to `configmap` for more clarity.
The only function that is named `issomething` (without underscore) was `git_oid_iszero`. Rename it to `git_oid_is_zero` for consistency with the rest of the library.