Add upload command for file attachments

[devin-ai-integration]

Add upload command for file attachments

Summary

Implements a new upload CLI command that allows users to upload files to Devin sessions via the attachments API endpoint (POST https://api.devin.ai/v1/attachments). The command uploads a file and returns the attachment URL that can be used in session prompts with the ATTACHMENT:"<url>" format.

Changes:

• Added upload_file() helper function for API interaction (60s timeout for uploads)
• Added upload CLI command with --output (json/table) and --format-prompt flags
• Added 5 comprehensive tests covering success and error cases (41 total tests pass)
• Updated README.md with usage examples and documentation

Verification:

• ✅ All 41 automated tests pass (including 5 new upload tests)
• ✅ Manually tested with real API using multiple file types (text, JSON, CSV, Python)
• ✅ Tested both output formats and --format-prompt flag
• ✅ Error handling verified (file not found, API errors)

Review & Testing Checklist for Human

This is a low-risk change that follows existing CLI patterns, but requires end-to-end verification:

• End-to-end test: Upload a file using devin-cli upload <file>, then create a Devin session using the returned URL with ATTACHMENT:"<url>" format to verify Devin can actually access and use the uploaded file
• Large file testing: Test uploading larger files (e.g., images, PDFs) to verify the 60-second timeout is sufficient and there are no size limit issues
• Edge case testing: Try uploading files with special characters in names, or test permission/locked file scenarios to ensure error messages are helpful

Notes

• The implementation follows the same patterns as existing commands (create, get, message)
• No new dependencies added (uses existing click and requests)
• The API returns URLs in quoted format (e.g., "https://..."), which is automatically stripped
• Files are opened in binary mode as required by the multipart/form-data upload

Devin Session: https://app.devin.ai/sessions/91d7514b99244be9a28804450a01cf51
Requested by: @parkerduff (parker.duff@codeium.com)

[devin-ai-integration]

🤖 Devin AI Engineer

I'll be helping with this pull request! Here's what you should know:

✅ I will automatically:

• Address comments on this PR. Add '(aside)' to your comment to have me ignore it.
• Look at CI failures and help fix them

Note: I can only respond to comments from users who have write access to this repository.

⚙️ Control Options:

• Disable automatic comment and CI monitoring