removing and adding keys must be atomic

If we delegate this to multiple seprarate objects (e.g. using __line) and the
config run is interrupted after applying only some of them we may leave the
target in some random state.
We may have even locked ourself out of the target.

So remove and add keys ourself so either none are all changes are
applied.

Signed-off-by: Steven Armstrong <steven@icarus.ethz.ch>

cdist/conf/type/__ssh_authorized_key/gencode-remote

@@ -18,31 +18,36 @@
 # along with cdist. If not, see <http://www.gnu.org/licenses/>.
 #
 
-file="$(cat "$__object/parameter/file")"
-state="$(cat "$__object/parameter/state")"
-mkdir "$__object/files"
-
-_cksum() {
-   echo "$1" | cksum | cut -d' ' -f 1
-}
-
-_do_line() {
+remove_line() {
    file="$1"
    line="$2"
-   state="$3"
-   line_id="$(_cksum "$file")-$(_cksum "$line")"
-
-   set -- "$line_id"
-   set -- "$@" --file "$file"
-   set -- "$@" --line "$line"
-   set -- "$@" --state "$state"
-   # Ensure __line does not read stdin
-   __line "$@" < /dev/null
+   cat << DONE
+tmpfile=\$(mktemp ${file}.cdist.XXXXXXXXXX)
+# preserve ownership and permissions of existing file
+if [ -f "$file" ]; then
+   cp -p "$file" "\$tmpfile"
+fi
+grep -v -F -x '$line' '$file' > \$tmpfile || true
+mv -f "\$tmpfile" "$file"
+DONE
 }
 
+add_line() {
+   file="$1"
+   line="$2"
+   # escape single quotes
+   line_sanitised=$(echo "$line" | sed -e "s/'/'\"'\"'/g")
+   printf '%s' "printf '%s\n' '$line_sanitised' >> $file"
+}
+
+
+file="$(cat "$__object/parameter/file")"
+mkdir "$__object/files"
+
 # Generate the entry as it should be
 (
    if [ -f "$__object/parameter/option" ]; then
+      # comma seperated list of options
       options="$(cat "$__object/parameter/option" | tr '\n' ',')"
       printf '%s ' "${options%*,}"
    fi
@@ -56,20 +61,37 @@ _do_line() {
    fi
 ) > "$__object/files/should"
 
-# Check for existing and conflicting entries and remove them
+# Remove conflicting entries if any
 if [ -s "$__object/explorer/entry" ]; then
-   # We have existing entries for this key.
-   # Check if any of them are in conflict to how the entry should be.
-   # Note that the file has to be sorted for comparison with `comm`.
+   # Note that the files have to be sorted for comparison with `comm`.
    sort "$__object/explorer/entry" > "$__object/files/is"
    comm -13 "$__object/files/should" "$__object/files/is" | {
-      # Remove conflicting entries
       while read entry; do
-         _do_line "$file" "$entry" absent
+         remove_line "$file" "$entry"
       done
    }
 fi
 
+# Determine the current state
+state_should="$(cat "$__object/parameter/state")"
+if grep -q -F -x "$entry" "$__object/explorer/entry"; then
+   state_is="present"
+else
+   state_is="absent"
+fi
+
 # Manage the actual entry as it should be
+if [ "$state_should" = "$state_is" ]; then
+   # Nothing to do
+   exit 0
+fi
+
 entry="$(cat "$__object/files/should")"
-_do_line "$file" "$entry" "$state"
+case "$state_should" in
+   present)
+      add_line "$file" "$entry"
+   ;;
+   absent)
+      remove_line "$file" "$entry"
+   ;;
+esac