Expose skip_existing setting to the end-users

Author: webknjaz

README.md

@@ -111,6 +111,25 @@ check with:
      verify_metadata: false
 ```
 
+### Tolerating release package file duplicates
+
+Sometimes, when you publish releases from multiple places, your workflow
+may hit race conditions. For example, when publishing from multiple CIs
+or even having workflows with the same steps triggered withing GitHub
+Actions CI/CD for different events concerning the same high-level act.
+
+To facilitate this use-case, you may use `skip_existing` (disabled by
+default) setting as follows:
+
+```yml
+   with:
+     skip_existing: true
+```
+
+> **Pro tip**: try to avoid enabling this setting where possible. If you
+have steps for publishing to both PyPI and TestPyPI, consider only using
+it for the latter, having the former fail loudly on duplicates.
+
 ## License
 
 The Dockerfile and associated scripts and documentation in this project

action.yml

@@ -20,6 +20,12 @@ inputs:
     description: Check metadata before uploading
     required: false
     default: true
+  skip_existing:
+    description: >-
+      Do not fail if a Python package distribution
+      exists in the target package index
+    required: false
+    default: false
 branding:
   color: yellow
   icon: upload-cloud
@@ -32,3 +38,4 @@ runs:
   - ${{ inputs.repository_url }}
   - ${{ inputs.packages_dir }}
   - ${{ inputs.verify_metadata }}
+  - ${{ inputs.skip_existing }}

twine-upload.sh

@@ -37,8 +37,13 @@ if [[ ${INPUT_VERIFY_METADATA,,} != "false" ]] ; then
     twine check ${INPUT_PACKAGES_DIR%%/}/*
 fi
 
+TWINE_EXTRA_ARGS=
+if [[ ${INPUT_SKIP_EXISTING,,} != "false" ]] ; then
+    TWINE_EXTRA_ARGS=--skip-existing
+fi
+
 
 TWINE_USERNAME="$INPUT_USER" \
 TWINE_PASSWORD="$INPUT_PASSWORD" \
 TWINE_REPOSITORY_URL="$INPUT_REPOSITORY_URL" \
-  exec twine upload ${INPUT_PACKAGES_DIR%%/}/*
+  exec twine upload ${TWINE_EXTRA_ARGS} ${INPUT_PACKAGES_DIR%%/}/*