Add 'shrinky' mode for path in window title

dotfiles/bash/post.bashrc

@@ -100,6 +100,7 @@ __bashum__wdir() {
     #
     local mode=${1:-normal}
     case $mode:$PWD in
+        shrinky:*)              __bashum__shrinkypath "$PWD" ;;
         normal:*)               echo "${PWD/$HOME/\~}" ;;
         short:$HOME)            echo "~" ;;
         short:$HOME/??????????) echo "${PWD/$HOME/\~}" ;;
@@ -109,6 +110,74 @@ __bashum__wdir() {
     esac
 }
 
+__bashum__shrinkypath() {
+    #
+    # Convert path $1 to small path
+    #
+    local path=$1
+    case $path in
+        $HOME)      echo "~"; return ;;
+        $HOME/*)    echo -n "~"; __bashum__shrink_relpath "${path#$HOME/}" ;;
+        *)          echo "$path"; return ;;
+    esac
+}
+
+__bashum__shrink_relpath() {
+    #
+    # Shrink relative path according to rules
+    #
+    # Rules are:
+    #
+    #  * if path has 7 chars or less, it's left as is and printed;
+    #  * else if there is only one element, it's left as is, and path is printed'
+    #  * else if there are three or more elements, elements
+    #    between first and last are replaced by '...',
+    #  * if the first element has 3 chars or less, it's left as is
+    #    and path is printed,
+    #  * else, the first element is
+    #      * broken into words by period,
+    #      * and each word, if longer than 2 characters,
+    #        is shortened to its first character followed by '...'
+    #      * and the shortened elements are joined back by period,
+    #  * finally the path is printed (first element shortened. '...', and
+    #    last element intact)
+    #
+    local path=$1
+    local elems
+    local frst
+    local last
+    local elnum
+    test "${#path}" -le 7 && echo -n "$path" && return 0
+    elems=(${path//// }); elnum=${#elems[@]}
+    frst=${elems[0]}
+    last=${elems[$((elnum-1))]}
+    case $elnum in
+        0) true ;;      # hardly possible (caught by -le 7 above)
+        1) echo -n "$path"; return ;;
+        2) __bashum__shrink_elem "$frst"; echo -n "/$last" ;;
+        *) __bashum__shrink_elem "$frst"; echo -n "/…/$last" ;;
+    esac
+}
+
+__bashum__shrink_elem() {
+    #
+    # Shrink element by words
+    #
+    local buff=$1
+    local word
+    local words
+    local head=true
+    words=(${buff//./ }); wnum=${#words[@]}
+    test "$wnum" -eq 0 && echo -n "$buff" && return 0
+    for word in "${words[@]}"; do
+        $head || { echo -n .; head=false; }
+        case $word in
+            ?|??)   echo -n "$word" ;;
+            *)      echo -n "${word:0:1}…" ;;
+        esac
+    done
+}
+
 #shellcheck disable=SC2016
 __bashum__mkpc() {
     #
@@ -121,7 +190,7 @@ __bashum__mkpc() {
             echo -n   "$(__bashum__mkicon) "
             echo -n   '$(__bashum__lastrv)'
             echo -n   "$(__bashum__mkhostid)"
-            echo -n   '$(__bashum__wdir short)'
+            echo -n   '$(__bashum__wdir shrinky)'
             echo -n   '\$'
             echo -n '\007"'
             ;;