Print helpful message when xavier CLI is called with no arguments

.github/workflows/main.yaml

@@ -15,6 +15,10 @@ jobs:
     steps:
       - uses: actions/checkout@v2
       - uses: docker://snakemake/snakemake:v6.8.2
+      - name: check CLI basics
+        run: |
+          ./xavier --help
+          ./xavier --version
       - name: Tumor-normal FastQ Dry Run
         run: |
           docker run -v $PWD:/opt2 snakemake/snakemake:v6.8.2 \

CHANGELOG.md

@@ -1,6 +1,7 @@
 ## development version
 
 - Create `CITATION.cff` to describe how to cite XAVIER. (#68, @kelly-sovacool)
+- Provide a more helpful error message when `xavier` is called with no arguments. (#75, @kelly-sovacool)
 - Minor documentation improvements. (#78, @kelly-sovacool)
 
 ## v3.0.2

xavier

@@ -780,6 +780,11 @@ def parsed_arguments():
 
 
 def main():
+    # show helpful error message when no arguments given
+    if len(sys.argv) == 1:
+        # Nothing was provided
+        fatal("Invalid usage: xavier [-h] [--version] ...")
+
     # Collect args for sub-command
     args = parsed_arguments()