Add absolute image path feature (#3)

If using this action for github pages, relative links break.  This adds a feature which allows absolute paths to be enabled when links are inserted into the markdown for compiled images.

You can now set the environment variable `ABSOLUTE_IMAGE_LINK` to flag the option:
- if unset, links remain relative
- if set, links are not absolute from using the output directory as a directory found in the repository root folder

entrypoint.sh

@@ -103,11 +103,18 @@ function c_md_mermaid {
     c_mermaid "${block_file}-${block_count}" "${2}/${dasherized}-${block_count}.png"
 
     # Compute relative path from the markdown to the tmp_dir
-    relative_path=$(realpath --relative-to="${input_dir}" "${2}/${dasherized}-${block_count}.png")
+    image_relative_path=$(realpath --relative-to="${input_dir}" "${2}/${dasherized}-${block_count}.png")
+    image_absolute_path="/${2}/${dasherized}-${block_count}.png"
+
+    if [[ -z "${ABSOLUTE_IMAGE_LINKS}" ]]; then
+      image_path="${image_relative_path}"
+    else
+      image_path="${image_absolute_path}"
+    fi
 
     # Insert the link to the markdown
     awk -v n="${block_count}" \
-        -v rel_path="${relative_path}" \
+        -v path="${image_path}" \
         -v hide_codeblocks="${HIDE_CODEBLOCKS}" \
         -f "${insert_markdown_awk}" \
         "${1}" > "${1}-temp"

insert-markdown.awk

@@ -6,7 +6,7 @@ BEGIN {
   i=0;
   start_comment="<!-- generated by mermaid compile action - START -->";
   end_comment="<!-- generated by mermaid compile action - END -->";
-  link="![~mermaid diagram " n "~](" rel_path ")";
+  link="![~mermaid diagram " n "~](" path ")";
 }
 
 # Rules to erase old generated code

package.json

@@ -17,6 +17,7 @@
   },
   "homepage": "https://github.com/neenjaw/mermaid-workflow-test#readme",
   "dependencies": {
-    "mermaid.cli": "^0.5.1"
+    "mermaid.cli": "^0.5.1",
+    "minimist": ">=0.2.1"
   }
 }