fix: apply UMASK env var via os.umask() at Python startup

[nitrobass24]

Summary

• The shell umask set in entrypoint.sh is not reliably inherited by the lftp subprocess through the setpriv exec chain in all container environments
• Downloaded files were created with the system default umask (0002 → 0664) instead of the user-configured value
• Fix reads UMASK env var directly in Python and calls os.umask() at startup, before pexpect spawns lftp

Fixes #109

Test plan

• Set UMASK=000 in Docker environment variables
• Queue a file for download
• Verify downloaded files have 0666 permissions (rw-rw-rw-) instead of 0664
• Verify downloaded directories have 0777 permissions
• Verify that omitting UMASK (empty string, the default) leaves system umask unchanged

Summary by CodeRabbit

• New Features
  • Added support for configuring process umask via an environment variable; the value is applied at startup and a warning is emitted for invalid values.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

Configuration used: Path: .coderabbit.yaml

Review profile: ASSERTIVE

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 1ddd7bb and cc8dead.

📒 Files selected for processing (1)

• src/python/seedsync.py

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📝 Walkthrough

Walkthrough

Adds UMASK handling at startup: reads UMASK from the environment, attempts octal parsing, applies it via os.umask(), and prints a stderr warning on invalid values. This runs before spawning child processes and does not change other control flow.

Changes

Cohort / File(s)	Summary
UMASK Configuration src/python/seedsync.py	Read UMASK env var, parse as octal, call os.umask() before creating child processes; prints a stderr warning if the value is invalid.

Sequence Diagram(s)

sequenceDiagram
    participant Env as Environment
    participant Main as Main process
    participant Child as Child processes

    Env->>Main: UMASK value (or absent)
    Main->>Main: parse UMASK as octal (try/except)
    alt valid UMASK
        Main->>Main: call os.umask(parsed_value)
    else invalid UMASK
        Main->>Main: print warning to stderr
    end
    Main->>Child: spawn child processes (inherit umask)

Loading

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Possibly related PRs

• Add UMASK environment variable to README #94: Documents the UMASK environment variable feature in README.
• Fix delete remote directory hang and add UMASK env var #92: Adds UMASK handling in Docker entrypoint/Dockerfile alongside runtime support.

Poem

🐰
I sniffed the env for a tiny mask,
Parsed the digits, a careful task.
If odd bits show, I whisper a scold,
Then set the tone before young processes unfold.
Hop — permissions tidy, neat, and bold. 🥕

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The PR title 'fix: apply UMASK env var via os.umask() at Python startup' accurately and specifically describes the main change: reading and applying the UMASK environment variable in Python before child process spawning.
Linked Issues check	✅ Passed	The code changes address the core requirement from issue #109 by implementing os.umask() in Python at startup, ensuring child processes inherit the configured UMASK before lftp is spawned via pexpect.
Out of Scope Changes check	✅ Passed	The changes are strictly scoped to the required functionality: reading UMASK from environment, parsing it as octal, applying via os.umask(), and handling invalid values with a stderr warning.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing Touches

• 📝 Generate docstrings (stacked PR)
• 📝 Generate docstrings (commit on current branch)

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch fix/umask-not-applied

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Inline comments:
In `@src/python/seedsync.py`:
- Line 412: Replace the .format-based print call in seedsync.py with an
f-string: locate the print call that emits the warning for an invalid UMASK (the
line using "_umask_str" and print(..., file=sys.stderr)) and rewrite the message
to use an f-string (e.g., f"WARNING: Invalid UMASK value {_umask_str!r},
ignoring") while preserving the target (sys.stderr) and surrounding behavior.

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ℹ️ Review info

Configuration used: Path: .coderabbit.yaml

Review profile: ASSERTIVE

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 6b586f2 and 1ddd7bb.

📒 Files selected for processing (1)

• src/python/seedsync.py