Add link.sh to create symbolic links to conf files.

It's used by Makefiles in subdirectories (like mail, shell, etc.) to create
symbolic links in ~/ to their configuration files so all configuration data
can be kept in one place.

diff --git a/link.sh b/link.sh
new file mode 100755 (executable)
index 0000000..6a92038
--- /dev/null
+++ b/link.sh
@@ -0,0 +1,34 @@
+#!/bin/sh
+
+# Creates a symbolic link for file $1 in dirname of $2 with name of basenmae
+# $2.
+#
+# `./link.sh example ~/.examplerc` creates a symbolic link to example
+# (wherever it is located) in ~/ named .examplerc.
+
+
+# Get all necessary paths.
+pwd=`pwd`
+base=`dirname "$2"`
+source=`echo -n "$pwd/$1" | sed "s|$base/||"`
+target=`basename "$2"`
+
+# Go to the directory where the link is going to be created.
+cd "$base"
+
+# Abort if the target file exists and is no symbolic link. Prevents
+# overwriting real files.
+if [ -e "$target" -a ! -h "$target" ]; then
+    echo "target '$target' exists already and is no symbolic link!" >&2
+    exit 1
+fi
+
+# Make sure the source exists.
+if [ ! -e "$source" ]; then
+    echo "source '$source' doesn't exist!" >&2
+    exit 1
+fi
+
+# Create the new symbolic link; remove the old one if necessary.
+rm -f "$target"
+ln -s "$source" "$target"