sd-path: expose XDG 'projects' user dir

As per:

https://blog.tenstral.net/2026/04/hello-projects-directory.html

man/sd_path_lookup.xml

@@ -68,6 +68,7 @@
         <constant>SD_PATH_USER_PUBLIC</constant>,
         <constant>SD_PATH_USER_TEMPLATES</constant>,
         <constant>SD_PATH_USER_DESKTOP</constant>,
+        <constant>SD_PATH_USER_PROJECTS</constant>,
 
         <constant>SD_PATH_SEARCH_BINARIES</constant>,
         <constant>SD_PATH_SEARCH_BINARIES_DEFAULT</constant>,

src/libsystemd/sd-path/sd-path.c

@@ -282,6 +282,9 @@ static int get_path(uint64_t type, char **buffer, const char **ret) {
         case SD_PATH_USER_DESKTOP:
                 return from_xdg_user_dir("XDG_DESKTOP_DIR", buffer, ret);
 
+        case SD_PATH_USER_PROJECTS:
+                return from_xdg_user_dir("XDG_PROJECTS_DIR", buffer, ret);
+
         case SD_PATH_SYSTEMD_UTIL:
                 *ret = PREFIX_NOSLASH "/lib/systemd";
                 return 0;

src/path/path-tool.c

@@ -61,6 +61,7 @@ static const char* const path_table[_SD_PATH_MAX] = {
         [SD_PATH_USER_PUBLIC]                                 = "user-public",
         [SD_PATH_USER_TEMPLATES]                              = "user-templates",
         [SD_PATH_USER_DESKTOP]                                = "user-desktop",
+        [SD_PATH_USER_PROJECTS]                               = "user-projects",
 
         [SD_PATH_SEARCH_BINARIES]                             = "search-binaries",
         [SD_PATH_SEARCH_BINARIES_DEFAULT]                     = "search-binaries-default",

src/systemd/sd-path.h

@@ -132,6 +132,8 @@ __extension__ enum {
         SD_PATH_USER_CREDENTIAL_STORE_ENCRYPTED,
         SD_PATH_USER_SEARCH_CREDENTIAL_STORE_ENCRYPTED,
 
+        SD_PATH_USER_PROJECTS,
+
         _SD_PATH_MAX,
         _SD_PATH_INVALID = UINT64_MAX
 };

test/units/TEST-74-AUX-UTILS.path.sh

@@ -39,6 +39,7 @@ XDG_DOCUMENTS_DIR="$HOME/top/secret/documents"
 XDG_MUSIC_DIR="/tmp/vaporwave"
 XDG_PICTURES_DIR="$HOME/Pictures"
 XDG_VIDEOS_DIR="$HOME/🤔"
+XDG_PROJECTS_DIR="$HOME/my-projects"
 EOF
 
 systemd-path --help
@@ -66,12 +67,13 @@ assert_eq "$(systemd-path user-pictures)" "/root/Pictures"
 assert_eq "$(systemd-path user-public)" "/root/cat-pictures"
 assert_eq "$(systemd-path user-templates)" "/templates"
 assert_eq "$(systemd-path user-videos)" "/root/🤔"
+assert_eq "$(systemd-path user-projects)" "/root/my-projects"
 
 # Remove the user-dirs.dir file and check the defaults
 rm -fv "$USER_DIRS_CONF"
 [[ ! -e "$USER_DIRS_CONF" ]]
 assert_eq "$(systemd-path user-desktop)" "/root/Desktop"
-for dir in "" documents download music pictures public templates videos; do
+for dir in "" documents download music pictures public templates videos projects; do
     assert_eq "$(systemd-path "user${dir:+-$dir}")" "/root"
 done