pd: support optional argument about which entry to pop.

* cdlog.sh (cdlog.pop): Rewritten to take argument 1-9, and
iterate from there.

* README.md: Documented.

2 files changed, 28 insertions, 11 deletions

diff --git a/README.md b/README.md
index 6b96ef4..c25ef67 100644
--- a/README.md
+++ b/README.md
@@ -29,9 +29,11 @@ arguments, it rotates among those. The directory is changed to the
 by the second item, the second by the third and so on. The last item
 receives the previously current directory.
 
-* `pd` (pop dir) is an alias for a command which changes to the most recent
-directory in the log, and removes that entry from the log. The second
-most recent directory becomes most recent and so on.
+* `pd` (pop dir) is an alias for a command which changes to (by default) the
+most recent directory in the log, and removes that entry from the log. The second most
+recent directory becomes most recent and so on. If it is given an argument
+value in the range 1 to 9, it changes to the specified entry, and removes it,
+moving the others down to close the gap. Thus `pd 1` is equivalent to `pd`.
 
 * `cdlog` function shows a listing of the four most recent entries in the
 log, or all nine if given the `-l` argument. The `cl` command is an alias for
diff --git a/cdlog.sh b/cdlog.sh
index 272d42e..cf10868 100644
--- a/cdlog.sh
+++ b/cdlog.sh
@@ -91,17 +91,32 @@ cdlog.rot()
 # from the log.
 cdlog.pop()
 {
-  if [ -n "$c1" ] && command cd "$c1"; then
-    c1=$c2; c2=$c3; c3=$c4
-    c4=$c5; c5=$c6; c6=$c7
-    c7=$c8; c8=$c9;
-
-    c9=
+  local d=("" "$c1" "$c2" "$c3" "$c4" "$c5" "$c6" "$c7" "$c8" "$c9")
+  local n=1
+  local i
 
-    cdlog.nicks
+  unset d[0]
 
-    printf "%s\n" "$PWD"
+  if [ $# -gt 0 ] ; then
+    n=$1; shift
   fi
+
+  case $n in
+  ( [1-9] )
+    if command cd "${d[$n]}" ; then
+      for ((i = n; i <= 8; i++)); do
+        d[$i]=${d[$((i + 1))]}
+      done
+      d[9]=
+      cdlog.args "${d[@]}"
+      printf "%s\n" "$PWD"
+    fi
+    ;;
+  ( * )
+    printf "cdlog.pop: bad argument: %s\n" "$n"
+    return 1
+    ;;
+  esac
 }
 
 # Print four recent cdlog entries.