If fetching from an anonymous remote via its URL, then the URL gets written into the FETCH_HEAD reference. This is mainly done to give valuable context to some commands, like for example git-merge(1), which will put the URL into the generated MERGE_MSG. As a result, what gets written into FETCH_HEAD may become public in some cases. This is especially important considering that URLs may contain credentials, e.g. when cloning 'https://foo:bar@example.com/repo' we persist the complete URL into FETCH_HEAD and put it without any kind of sanitization into the MERGE_MSG. This is obviously bad, as your login data has now just leaked as soon as you do git-push(1). When writing the URL into FETCH_HEAD, upstream git does strip credentials first. Let's do the same by trying to parse the remote URL as a "real" URL, removing any credentials and then re-formatting the URL. In case this fails, e.g. when it's a file path or not a valid URL, we just fall back to using the URL as-is without any sanitization. Add tests to verify our behaviour.
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.
We treat each refspec on its own, but the code currently overwrites the contents of FETCH_HEAD so we end up with the entries for the last refspec we processed. Instead, truncate it before performing the updates and append to it when updating the references.
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.
The `path_repository` variable is actually confusing to think about, as it is not always clear what the repository actually is. It may either be the path to the folder containing worktree and .git directory, the path to .git itself, a worktree or something entirely different. Actually, the intent of the variable is to hold the path to the gitdir, which is either the .git directory or the bare repository. Rename the variable to `gitdir` to avoid confusion. While at it, also rename `path_gitlink` to `gitlink` to improve consistency.
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