semver increment in shell script

Question

I am trying to implement a solution to increment a version. Here's what I have come up with:

#!/bin/sh -x

VAR=1.0.1 # retrieved from Gitlab API

case $1 in
patch)
    TAG=${VAR%.*}.$((${VAR##*.} + 1))
    ;;

major)
    TAG=$((${VAR%%.*} + 1)).0.0
    ;;

*)
    tmp=${VAR%.*}
    minor=${tmp#*.}
    TAG=${VAR%%.*}.$((minor + 1)).0
    ;;
esac

echo $TAG

major & patch work as expected; however, I'm facing problems incrementing minor.

When bumping 1.0.1, the minor should be 1.1.0; however, my code produces 1.2.0. What am I doing wrong?

Some more info, the script is executed inside a GitlabCI pipeline.

Edit: Updated the code with the suggested answer from @jhnc

Answer 1

Your computation for incrementing minor is:

TAG=${VAR%%.*}.$((${VAR##*.} + 1)).0

However, ${VAR##*.} gives the patch value, not the minor value, and thus your incorrect result.

To extract minor, you can use a temporary variable:

tmp=${VAR%.*}
minor=${tmp#*.}
TAG=${VAR%%.*}.$((minor + 1)).0

Alternatively, it may be more readable to set IFS and split the string on dots:

TAG=$(
   echo "$VAR" | while IFS=. read major minor patch; do
       # add sanity-checks here
       case "$1" in
          patch)
             echo "$major.$minor.$((patch+1))"
             ;;
          major)
             echo "$((major+1).0.0"
             ;;
          minor|*)
             echo "$major.$((minor+1)).0" 
             ;;
       esac
   done
)

You should probably add sanity-checks to ensure VAR is actually of form "digits dot digits dot digits".