Introduce `git_path_validate_filesystem` which validates (absolute) on-disk paths and `git_path_validate_workdir` to perform validations on (absolute) working directory paths. These functions are useful as there may be system limitations on on-disk paths, particularly on Windows (for example, enforcing MAX_PATH). For working directory paths, these limitations may be per-repository, based on the `core.longpaths` configuration setting.
This change adds all the necessary locking to the odb to avoid races in the backends. Part of: #5592
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.
Since we were not expecting this config entry to contain a string, we would fail as soon as its (cached) value would be accessed. Hence, provide some constants for the 4 states we use, and account for "always" when we decide to reflog changes.
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.
Callers of `git_config__cvar` already handle the case where the function returns an error due to a failed configuration variable lookup, but we are actually swallowing errors when calling `git_config__lookup_entry` inside of the function. Fix this by returning early when `git_config__lookup_entry` returns an error. As we call `git_config__lookup_entry` with `no_errors == false` which leads us to call `get_entry` with `GET_NO_MISSING` we will not return early when the lookup fails due to a missing entry. Like this we are still able to set the default value of the cvar and exit successfully.