We want to do this in order to get FETCH_HEAD to be empty when we start updating it due to fetching from the remote.
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.
Update to forced checkout and untracked files
Only ignore `EBUSY` from `rmdir` when the `GIT_RMDIR_SKIP_NONEMPTY` bit is set.
When the `git_futils_mmap_ro_file` function encounters an error after the file has been opened, it will do a simple returns. Instead, we should close the opened file descriptor to avoid a leak. This commit fixes the issue.
When executing `git_futils_mmap_ro_file`, we first try to guess whether the file is mmapable at all. Part of this check is whether the file is too large to be mmaped, which can be true on systems with 32 bit `size_t` types. The check is performed by first getting the file size wtih `git_futils_filesize` and then checking whether the returned size can be represented as `size_t`, returning an error if so. While this test also catches the case where the function returned an error (as `-1` is not representable by `size_t`), we will set the misleading error message "file too large to mmap". But in fact, a negative return value from `git_futils_filesize` will be caused by the inability to fstat the file. Fix the error message by handling negative return values separately and not overwriting the error message in that case.
git_futils: don't O_EXCL and O_TRUNC
fsync all the things
`O_EXCL` and `O_TRUNC` are mutually exclusive flags to open(2); you can't truncate a file if you're asserting that it can't exist in the first place. Drop `O_TRUNC`.