functions: allow add_symlink to only take a single arg

In the case of a single arg, use readlink(1) to resolve the target of
the symlink. Document this, and additionally note the lack of guarantee
about the target of the symlink.

Signed-off-by: Dave Reisner <dreisner@archlinux.org>

2 files changed, 24 insertions, 10 deletions

diff --git a/functions b/functions
index 4f25a86..8a270fd 100644
--- a/functions
+++ b/functions
@@ -402,22 +402,33 @@ add_dir() {
 }
 
 add_symlink() {
-    # Add a symlink to the initcpio image.
+    # Add a symlink to the initcpio image. There is no checking done
+    # to ensure that the target of the symlink exists.
     #   $1: pathname of symlink on image
-    #   $2: absolute path to target of symlink
+    #   $2: absolute path to target of symlink (optional, can be read from $1)
 
-    (( $# == 2 )) || return 1
+    local name_=$1 target_=$2
 
-    add_dir "${1%/*}"
+    (( $# == 1 || $# == 2 )) || return 1
+
+    if [[ -z $target_ ]]; then
+        target_=$(readlink -f "$name_")
+        if [[ -z $target_ ]]; then
+            error 'invalid symlink: %s' "$name_"
+            return 1
+        fi
+    fi
+
+    add_dir "${name_%/*}"
 
     if (( ! QUIET )); then
         if [[ -L $BUILDROOT$1 ]]; then
-            plain "overwriting symlink %s -> %s" "$1" "$2"
+            plain "overwriting symlink %s -> %s" "$name_" "$target_"
         else
-            plain "adding symlink: %s -> %s" "$1" "$2"
+            plain "adding symlink: %s -> %s" "$name_" "$target_"
         fi
     fi
-    ln -sfn "$2" "$BUILDROOT$1"
+    ln -sfn "$target_" "$BUILDROOT$name_"
 }
 
 add_file() {
diff --git a/mkinitcpio.8.txt b/mkinitcpio.8.txt
index a33869d..efa385f 100644
--- a/mkinitcpio.8.txt
+++ b/mkinitcpio.8.txt
@@ -131,10 +131,13 @@ functions exist to facilitate this.
 	calling *add_file*, *add_dir*, and *add_symlink* accordingly. This function
 	will not follow symlinks, nor will it add the targets of symlinks.
 
-*add_symlink* 'path' 'link-target'::
+*add_symlink* 'path' [ 'link-target' ]::
 
-	Adds a symlink to the image at the specified `path`, pointing to the specified
-	`link-target`.
+	Adds a symlink to the image at the specified `path`, optionally pointing to
+	the specified `link-target`. If the `link-target` is not provided, it is assumed
+	that this symlink exists in the real filesystem, and the target will be read
+	using readlink. There is no checking done to ensure that the target of the
+	symlink exists, and symlinks will not be followed recursively.
 
 *add_all_modules* [ '-f filter' ] *pattern*::