docs: use relative links

Allows for links to work both on systemd.io (or forks) and
when viewed on https://github.com/systemd/systemd/tree/main/docs

Note that the markdown links are converted by jekyll-relative-links[1]
to html. This plugin is enabled by default on github pages[2][3].

Due to a bug in jekyll-relative-links – see
https://github.com/benbalter/jekyll-relative-links/issues/61 –
we need to avoid line-wrapped links when using relative markdown links.

[1] https://github.com/benbalter/jekyll-relative-links
[2] https://github.blog/2016-12-05-relative-links-for-github-pages/
[3] https://docs.github.com/en/pages/setting-up-a-github-pages-site-with-jekyll/about-github-pages-and-jekyll#plugins

1 files changed, 7 insertions, 8 deletions

diff --git a/docs/USER_RECORD.md b/docs/USER_RECORD.md
index da911d5e73..5308102944 100644
--- a/docs/USER_RECORD.md
+++ b/docs/USER_RECORD.md
@@ -14,8 +14,8 @@ pairs, encoded as JSON. Specifically:
 
 1. [`systemd-homed.service`](https://www.freedesktop.org/software/systemd/man/systemd-homed.service.html)
    manages `human` user home directories and embeds these JSON records
-   directly in the home directory images (see [Home
-   Directories](https://systemd.io/HOME_DIRECTORY) for details).
+   directly in the home directory images
+   (see [Home Directories](HOME_DIRECTORY.md) for details).
 
 2. [`pam_systemd`](https://www.freedesktop.org/software/systemd/man/pam_systemd.html)
    processes these JSON records for users that log in, and applies various
@@ -71,14 +71,13 @@ the following extensions are envisioned:
 
 4. Default parameters for backup applications and similar
 
-Similar to JSON User Records there are also [JSON Group
-Records](https://systemd.io/GROUP_RECORD) that encapsulate UNIX groups.
+Similar to JSON User Records there are also
+[JSON Group Records](GROUP_RECORD.md) that encapsulate UNIX groups.
 
 JSON User Records may be transferred or written to disk in various protocols
 and formats. To inquire about such records defined on the local system use the
-[User/Group Lookup API via
-Varlink](https://systemd.io/USER_GROUP_API). User/group records may also be
-dropped in number of drop-in directories as files. See
+[User/Group Lookup API via Varlink](USER_GROUP_API.md). User/group records may
+also be dropped in number of drop-in directories as files. See
 [`nss-systemd(8)`](https://www.freedesktop.org/software/systemd/man/nss-systemd.html)
 for details.
 
@@ -215,7 +214,7 @@ object. The following fields are currently defined:
 UNIX user name. This field is the only mandatory field, all others are
 optional. Corresponds with the `pw_name` field of of `struct passwd` and the
 `sp_namp` field of `struct spwd` (i.e. the shadow user record stored in
-`/etc/shadow`). See [User/Group Name Syntax](https://systemd.io/USER_NAMES) for
+`/etc/shadow`). See [User/Group Name Syntax](USER_NAMES.md) for
 the (relaxed) rules the various systemd components enforce on user/group names.
 
 `realm` → The "realm" a user is defined in. This concept allows distinguishing