+appropriate values for fake bare Git repositories.
+
+## CONFIG
+
+There are several ways to turn the various knobs on `vcsh`. In order of
+ascending precedence, they are:
+
+* `VARIABLE=foo vcsh`
+* </etc/vcsh/config>
+* <$XDG_CONFIG_HOME/vcsh/config>
+* `vcsh -c <file>`
+
+Please note that those files are sourced. Any and all commands will be
+executed in the context of your shell.
+
+Interesting knobs you can turn:
+
+* <$VCSH_GITATTRIBUTES>:
+ Can be <none>, or any other value.
+
+ <none> will not maintain Git attributes in a special location.
+
+ If set to any other value, repo-specific gitattributes files will be maintained.
+
+ Defaults to <none>.
+
+* <$VCSH_GITIGNORE>:
+ Can be <exact>, <none>, or <recursive>.
+
+ <exact> will seed the repo-specific ignore file with all file and directory
+ names which `git ls-files` returns.
+
+ <none> will not write any ignore file.
+
+ <recursive> will descend through all directories recursively additionally to
+ the above.
+
+ Defaults to <exact>.
+
+* <$VCSH_VCSH_WORKTREE>:
+ Can be <absolute>, or <relative>.
+
+ <absolute> will set an absolute path; defaulting to <$HOME>.
+
+ <relative> will set a path relative to <$GIT_DIR>.
+
+ Defaults to <absolute>.
+
+Less interesting knobs you could turn:
+
+* <$VCSH_DEBUG>:
+ Enter debug mode.
+
+* <$XDG_CONFIG_HOME>:
+ As specified in the 'XDG Base Directory Specification', see
+ <http://standards.freedesktop.org/basedir-spec/basedir-spec-latest.html>
+
+ Defaults to <$HOME/.config>.
+
+* <$VCSH_REPO_D>:
+ The directory where repositories are read from and stored.
+
+ Defaults to <$XDG_CONFIG_HOME/vcsh/repo.d>.
+
+* <$VCSH_HOOK_D>:
+ The directory where hooks are read from.
+
+ Defaults to <$XDG_CONFIG_HOME/vcsh/hooks-enabled>.
+
+* <$VCSH_BASE>:
+ The directory where repositories are checked out to.
+
+ Defaults to <$HOME>.
+
+
+## HOOK SYSTEM
+
+`vcsh` provides a hook system. Hook scripts must be executable and should be
+placed in <$XDG_CONFIG_HOME/vcsh/hooks-available>. From there, they can be
+soft-linked into <$XDG_CONFIG_HOME/vcsh/hooks-enabled>; `vcsh` will only
+execute hooks that are in this directory.
+
+Hooks follow a simple format. <pre-run> will be run before anything is run.
+If you want to have more than one script for a certain hook, just append
+any kind of string to order them. A system of <pre-run>, <pre-run.10>,
+<pre-run.20> etc is suggested; other options would be <pre-run-10> or
+<pre-run.sh>. A dot after the hook name is optional.
+
+If you want to create hooks for a specific <vcsh> repository, simply prepend
+the repository's name, followed by a dot, i.e. <zsh.pre-run>. Otherwise, the
+same rules as above apply. The dot between the repository's name and the hook
+is mandatory, though.
+
+Available hooks are <pre-clone>, <post-clone>, <post-clone-retired>,
+<pre-command>, <post-command>, <pre-enter>, <post-enter>, <pre-init>,
+<post-init>, <pre-pull>, <post-pull>, <pre-push>, <post-push>, <pre-run>,
+<post-run>, <pre-upgrade>, and <post-upgrade>.
+If you need more, vcsh is trivial to patch, but please let upstream know so
+we can ship them by default.
+
+## OVERLAY SYSTEM
+
+`vcsh` also provides an overlay system. Similar to hooks, the recommended
+locations are <$XDG_CONFIG_HOME/vcsh/overlays-available> and
+<$XDG_CONFIG_HOME/vcsh/overlays-enabled>.
+
+Overlays follow the same rules as hooks and you are free to overwrite any
+and all functions. Same as hooks, you can use global or repository-specific
+overlays by using either <$VCSH_OVERLAY_D/$VCSH_COMMAND> or
+<$VCSH_OVERLAY_D/$VCSH_REPO_NAME.$VCSH_COMMAND>.
+
+Please note that nothing stops you from, e.g. overwriting `status()` in
+<$VCSH_OVERLAY_D/commit>. As the overlays will be sourced and you are
+replacing arbitrary functions, any and all features may stop working, or you
+may even lose data.
+
+You have been warned.