Compute lines of *unstaged* changes in prompt

Parse `git diff --shortstat` to get the line count of *unstaged* changes.

Improvements of the git related stuff are still possible, using more
plumbing commands, like:
* `git diff-index --quiet HEAD` to check for uncommitted changes (branch
  color), rather than relying on the `git diff --shortstat HEAD`
* `git ls-files --exclude-standard --others` to check for untracked
  files

liquidprompt

@@ -773,16 +773,32 @@ _lp_git_branch_color()
             fi
         fi
 
-        local shortstat
         local ret
+        local shortstat # only to check for uncommitted changes
         shortstat="$(LC_ALL=C \git diff --shortstat HEAD 2>/dev/null)"
+
         if [[ -n "$shortstat" ]] ; then
+            local u_stat # shorstat of *unstaged* changes
+            u_stat="$(LC_ALL=C \git diff --shortstat 2>/dev/null)"
+            u_stat=${u_stat/*changed, /} # removing "n file(s) changed"
+
+            local i_lines # inserted lines
+            if [[ "$u_stat" = *insertion* ]] ; then
+                i_lines=${u_stat/ inser*}
+            else
+                i_lines=0
+            fi
+
+            local d_lines # deleted lines
+            if [[ "$u_stat" = *deletion* ]] ; then
+                d_lines=${u_stat/*\(+\), }
+                d_lines=${d_lines/ del*/}
+            else
+                d_lines=0
+            fi
+
             local has_lines
-            #has_lines=$(\git diff --numstat 2>/dev/null | awk 'NF==3 {plus+=$1; minus+=$2} END {printf("+%d/-%d\n", plus, minus)}')
-            has_lines=${shortstat/*changed, /}
-            has_lines=${has_lines/ inser*, /\/-}
-            has_lines=${has_lines/ del*/}
-            [[ "$shortstat" = *insertion* ]] && has_lines="+${has_lines/ inser*/}" || has_lines="-$has_lines"
+            has_lines="+$i_lines/-$d_lines"
 
             if [[ "$has_commit" -gt "0" ]] ; then
                 # Changes to commit and commits to push