The old POSIX regex API has been superseded by our new regexp API. Convert all users to make use of the new one.
Prefix all the calls to the the regexec family of functions with `p_`. This allows us to swap out all the regular expression functions with our own implementation. Move the declarations to `posix_regex.h` for simpler inclusion.
Move to the `git_error` name in the internal API for error-related functions.
We use the term "invalid" to refer to bad or malformed data, eg `GIT_REF_INVALID` and `GIT_EINVALIDSPEC`. Since we're changing the names of the `git_object_t`s in this release, update it to be `GIT_OBJECT_INVALID` instead of `BAD`.
Use the new object_type enumeration names within the codebase.
Replace remaining uses of the `git__strtol32` function. While these uses are all safe as the strings were either sanitized or from a trusted source, we want to remove `git__strtol32` altogether to avoid future misuse.
A lot of compilers nowadays generate warnings when there are cases in a switch statement which implicitly fall through to the next case. To avoid this warning, the last line in the case that is falling through can have a comment matching a regular expression, where one possible comment body would be `/* fall through */`. An alternative to the comment would be an explicit attribute like e.g. `[[clang::fallthrough]` or `__attribute__ ((fallthrough))`. But GCC only introduced support for such an attribute recently with GCC 7. Thus, and also because the fallthrough comment is supported by most compilers, we settle for using comments instead. One shortcoming of that method is that compilers are very strict about that. Most interestingly, that comment _really_ has to be the last line. In case a closing brace follows the comment, the heuristic will fail.
Next to including several files, our "common.h" header also declares various macros which are then used throughout the project. As such, we have to make sure to always include this file first in all implementation files. Otherwise, we might encounter problems or even silent behavioural differences due to macros or defines not being defined as they should be. So in fact, our header and implementation files should make sure to always include "common.h" first. This commit does so by establishing a common include pattern. Header files inside of "src" will now always include "common.h" as its first other file, separated by a newline from all the other includes to make it stand out as special. There are two cases for the implementation files. If they do have a matching header file, they will always include this one first, leading to "common.h" being transitively included as first file. If they do not have a matching header file, they instead include "common.h" as first file themselves. This fixes the outlined problems and will become our standard practice for header and source files inside of the "src/" from now on.