Fix renaming using 'bb.sh edit -n'. Suppress 'which' errmsg.

edit(): The -n functionality (to rename files according to new title) was
broken. After renaming, files were accessed by the old name and not found,
or empty files were recreated under the old name, or both. Fixes:
- Move 'touch' commands for restoring time stamps to more opportune places.
- When renaming, save old file name to exclude it from $relevant_posts.

global_variables(): suppress GNU 'which' error message on setting markdown_bin.

bb.sh

@@ -159,7 +159,7 @@ global_variables() {
 
     # Markdown location. Trying to autodetect by default.
     # The invocation must support the signature 'markdown_bin in.md > out.html'
-    markdown_bin=$(which Markdown.pl || which markdown)
+    markdown_bin=$(which Markdown.pl 2>/dev/null || which markdown 2>/dev/null)
 }
 
 # Check for the validity of some variables
@@ -296,6 +296,7 @@ edit() {
     tags_before=$(tags_in_post "${1%%.*}.html")
     if [[ $2 == full ]]; then
         invoke_editor "$1"
+        touch -t "$touch_timestamp" "$1"
         filename=$1
     else
         if [[ ${1##*.} == md ]]; then
@@ -306,6 +307,7 @@ edit() {
             fi
             # editing markdown file
             invoke_editor "$1"
+            touch -t "$touch_timestamp" "$1"
             TMPFILE=$(markdown "$1")
             filename=${1%%.*}.html
         else
@@ -320,21 +322,23 @@ edit() {
         fi
         rm "$filename"
         if [[ $2 == keep ]]; then
+            old_filename=''
             parse_file "$TMPFILE" "$edit_timestamp" "$filename"
         else
+            old_filename=$filename                  # save old filename to exclude it from $relevant_posts
             parse_file "$TMPFILE" "$edit_timestamp" # this command sets $filename as the html processed file
             [[ ${1##*.} == md ]] && mv "$1" "${filename%%.*}.md" 2>/dev/null
         fi
         rm "$TMPFILE"
+        touch -t "$touch_timestamp" "$filename"
     fi
-    touch -t "$touch_timestamp" "$filename"
-    touch -t "$touch_timestamp" "$1"
     chmod 644 "$filename"
     echo "Posted $filename"
     tags_after=$(tags_in_post "$filename")
     relevant_tags=$(sort -u <<< "$tags_before"$'\n'"$tags_after")
     if [[ -n $relevant_tags ]]; then
         relevant_posts=$(posts_with_tags $relevant_tags)$'\n'$filename
+        [[ -n $old_filename ]] && relevant_posts=$(grep -vFx "$old_filename" <<<"$relevant_posts")
         rebuild_tags $relevant_posts --tags $relevant_tags
     fi
 }