zshrc: extend dchange() to support apt-get and multiple package names

Since apt v0.8.11 it's possible to use "apt-get changelog $package"
as well. While at it support displaying changelogs for multiple
packages.

etc/zsh/zshrc

@@ -2544,26 +2544,31 @@ sll() {
 #   PAGER='less -Mr' - If so, the use of $PAGER here needs fixing
 # with respect to wordsplitting. (ie. ${=PAGER})
 if check_com -c $PAGER ; then
-    #f3# View Debian's changelog of a given package
+    #f3# View Debian's changelog of given package(s)
     dchange() {
         emulate -L zsh
-        if [[ -r /usr/share/doc/$1/changelog.Debian.gz ]] ; then
-            $PAGER /usr/share/doc/$1/changelog.Debian.gz
-        elif [[ -r /usr/share/doc/$1/changelog.gz ]] ; then
-            $PAGER /usr/share/doc/$1/changelog.gz
-        else
-            if check_com -c aptitude ; then
-                echo "No changelog for package $1 found, using aptitude to retrieve it."
-                if isgrml ; then
-                    aptitude -t unstable changelog $1
+        [[ -z "$1" ]] && printf 'Usage: %s <package_name(s)>\n' "$0" && return 1
+
+        for file in "$@" ; do
+            if [[ -r /usr/share/doc/${file}/changelog.Debian.gz ]] ; then
+                $PAGER /usr/share/doc/${file}/changelog.Debian.gz
+            elif [[ -r /usr/share/doc/${file}/changelog.gz ]] ; then
+                $PAGER /usr/share/doc/${file}/changelog.gz
+            elif [[ -r /usr/share/doc/${file}/changelog ]] ; then
+                $PAGER /usr/share/doc/${file}/changelog
+            else
+                if check_com -c aptitude ; then
+                    echo "No changelog for package(s) $file found, using aptitude to retrieve it."
+                    aptitude changelog "$file"
+                elif check_com -c apt-get ; then
+                    echo "No changelog for package(s) $file found, using apt-get to retrieve it."
+                    apt-get changelog "$file"
                 else
-                    aptitude changelog $1
+                    echo "No changelog for package(s) $file found, sorry."
+                    return 1
                 fi
-            else
-                echo "No changelog for package $1 found, sorry."
-                return 1
             fi
-        fi
+        done
     }
     _dchange() { _files -W /usr/share/doc -/ }
     compdef _dchange dchange