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.
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.
Move to the `git_error` name in the internal API for error-related functions.
Allow for a custom conflict marker size, allowing callers to override the default size of the "<<<<<<<" and ">>>>>>>" markers in the conflicted output file.
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.
Error messages should be sentence fragments, and therefore: 1. Should not begin with a capital letter, 2. Should not conclude with punctuation, and 3. Should not end a sentence and begin a new one
The `merge_file__xdiff` function checks if either `ours` or `theirs` is `NULL`. The function is to be called with existing files, though, and in fact already unconditionally dereferences both pointers. Remove the unnecessary check to silence warnings.
Consumers can now register custom merged drivers with `git_merge_driver_register`. This allows consumers to support the merge drivers, as configured in `.gitattributes`. Consumers will be asked to perform the file-level merge when a custom driver is configured.