Update entrypoint.sh to allow initial version of bumping

entrypoint.sh

@@ -61,17 +61,29 @@ preTagFmt="^v?[0-9]+\.[0-9]+\.[0-9]+(-$suffix\.[0-9]+)?$"
 case "$tag_context" in
     *repo*) 
         taglist="$(git for-each-ref --sort=-v:refname --format '%(refname:lstrip=2)' | grep -E "$tagFmt")"
-        tag="$(semver $taglist | tail -n 1)"
+        if [ -n "$taglist"]
+        then
+            tag="$(semver $taglist | tail -n 1)"
+        fi
 
         pre_taglist="$(git for-each-ref --sort=-v:refname --format '%(refname:lstrip=2)' | grep -E "$preTagFmt")"
-        pre_tag="$(semver $pre_taglist | tail -n 1)"
+        if [ -n "$taglist"]
+        then
+            pre_tag="$(semver $pre_taglist | tail -n 1)"
+        fi
         ;;
     *branch*) 
         taglist="$(git tag --list --merged HEAD --sort=-v:refname | grep -E "$tagFmt")"
-        tag="$(semver $taglist | tail -n 1)"
+        if [ -n "$taglist"]
+        then
+            tag="$(semver $taglist | tail -n 1)"
+        fi
 
         pre_taglist="$(git tag --list --merged HEAD --sort=-v:refname | grep -E "$preTagFmt")"
-        pre_tag=$(semver $pre_taglist | tail -n 1)
+        if [ -n "$taglist"]
+        then
+            pre_tag="$(semver $pre_taglist | tail -n 1)"
+        fi
         ;;
     * ) echo "Unrecognised context"; exit 1;;
 esac
@@ -86,15 +98,22 @@ then
     then
       pre_tag="$initial_version"
     fi
+    tag_commit="none"
+    pre_tag_commit="none"
 else
     log=$(git log $tag..HEAD --pretty='%B')
-fi
-
-# get current commit hash for tag
-tag_commit=$(git rev-list -n 1 $tag)
+
+    # get current commit hash for tag
+    tag_commit=$(git rev-list -n 1 $tag)
 
-# get current commit hash for pre_tag
-pre_tag_commit=$(git rev-list -n 1 $pre_tag)
+    if [ -n "$pre_tag" ]
+    then
+        # get current commit hash for pre_tag
+        pre_tag_commit=$(git rev-list -n 1 $pre_tag)
+    else
+        pre_tag_commit="none"
+    fi
+fi
 
 # get current commit hash
 commit=$(git rev-parse HEAD)
@@ -149,7 +168,7 @@ echo $part
 # prefix with 'v'
 if $with_v
 then
-	new="v$new"
+    new="v$new"
 fi
 
 if [ ! -z $custom_tag ]