refactor!(action): detect when in private branches

This removes the need to use the private-repo-workaround input.

README.md

@@ -1,12 +1,12 @@
 # Nix Flake outputs size
 
-Use `nix path-info` to query the size of flake outputs and produce a markdown report.
+Use `nix path-info` to query the size of flake outputs and produce a report.
 
-You can post this report as a comment to the PR associated with the current branch and/or export the report as a markdown artifact.
+This repost can be posted to a PR (as formatted markdown) and/or uploaded as a workflow artifact.
 
-Requires `nix`, `jq`, `curl`, `sed` and `coreutils` to be in path.
+Requires `nix`, `jq`, `curl`, `sed`, `gunzip`, `tar` and `coreutils` to be in the runner's path.
 
-## Usage
+## Example
 
 ```yaml
 - name: Generate size report
@@ -15,6 +15,11 @@ Requires `nix`, `jq`, `curl`, `sed` and `coreutils` to be in path.
     comment-on-pr: 'true'
     generate-artifact: 'false'
     artifact-name: 'size-report.md'
+    # If you want to enable comparisons set this to true
+    do-comparison: 'false'
+    job-name: '' # required if do-comparison is true
+    # This is the branch that will be compared against
+    base-branch: ${{ github.base_ref }} # or default branch if missing
 ```
 
 For more details see the [action.yaml](./action.yml) file.