fix(ignore-io): use GitHub gitignore templates

[vjymisal0]

Summary

git-ignore-io currently fetches templates through the Toptal-hosted gitignore.io endpoint, which can reject requests with Cloudflare. Use GitHub's public gitignore repository as the source instead. Template names are resolved case-insensitively so existing cached lists continue to work.

• Fetch the template list from GitHub's Contents API.
• Fetch individual templates from raw.githubusercontent.com.
• Preserve multi-template requests and update generated documentation.

Test plan

• bash -n bin/git-ignore-io
• ./check_integrity.sh ignore-io
• Manually fetched Python and Java templates, including from a legacy lowercase cache.

Fixes #1272

[spacewander]

Here's the AI review result:

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The PR replaces gitignore.io with GitHub's github/gitignore repo in git-ignore-io. The reviewer verified against live GitHub endpoints and found the core idea works, but two issues block merge:

High — Global/ templates are broken (silent 404s):

• ~70 of the most-used templates (Vim, Emacs, macOS, Windows, JetBrains, Xcode, VirtualEnv, etc.) live in the Global/ subdirectory, not the repo root
• The PR only lists/fetches root-level *.gitignore files, so git ignore-io vim — the exact example in the updated man page — silently returns nothing
• curl -fsSL swallows the 404, so users get zero output, no error
• This is a regression: gitignore.io previously served all of these

Medium — rate limits & silent failures:

• Unauthenticated GitHub Contents API = 60 req/hour, and gi() now hits it on every invocation even with a valid cache
• update_gi_list writes an empty cache file on failure, breaking -l/-L/-s until next successful -u
• git ignore-io -r typo truncates .gitignore to empty with no warning (pre-existing risk, now more likely due to silent 404s)

Minor:

• man/git-ignore-io.md example still shows the old toptal URL (would revert on regeneration); the updated .1/.html example URL is itself a 404
• "Initial gitignore.io list" banner at bin/git-ignore-io:86 not updated

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Proposed Fix Plan

1. Include Global/ templates: switch to the git trees API (git/trees/main?recursive=1) in one call, filter for *.gitignore, and store each file's full path (or build URLs from path) so both root and Global/ templates resolve
2. Respect the cache: only call the API when the cache is missing/expired or -u is passed, avoiding the 60 req/hour ceiling
3. Error handling: on curl failure, print an error to stderr and skip cache truncation / refuse -r write instead of silently emptying files
4. Docs: update the .md example, fix the 404 example URL (use e.g. Global/Vim.gitignore), and update the init banner string

One tradeoff to confirm: trees API responses are large (~1MB for the whole repo) — acceptable for a one-off -u refresh, which is why I'd cache and only fetch on demand.

[vjymisal0]

Thanks for the detailed review @spacewander. I switched list refreshes to the recursive git tree API so Global/* templates such as Global/Vim are cached and fetched correctly, and template generation now uses the cache instead of hitting GitHub on every invocation. Refreshes are atomic and report failures without overwriting a valid cache; --replace/--append also avoid modifying files when a requested template cannot be fetched. Updated the generated man pages and init banner. Verified with live -u, vim, and missing-template scenarios, plus bash syntax and diff checks. Pushed as bb9fb05.

[spacewander]

Main issue (must fix before merge)

Legacy caches resolve but then 404 — the PR's stated goal of keeping existing cached lists working isn't met:

• raw.githubusercontent.com is case-sensitive (Python.gitignore → 200, python.gitignore → 404)
• Legacy gitignore.io caches store all-lowercase names (python, vim, ...), so lookup succeeds but fetch 404s
• Stale/invalid caches are never auto-repaired — check_list_exist only refreshes missing files; a user whose last update_gi_list failed under old code has a cache full of Cloudflare HTML that's never refreshed

Proposed fix plan (for bin/git-ignore-io)

1. Legacy/invalid cache detection + refresh: in check_list_exist, treat the cache as invalid if it doesn't look like a GitHub template list (e.g. single comma-joined line, or no valid path entries) and force re-download. This fixes both lowercase legacy caches and HTML-poisoned caches in one shot.
2. Fallback retry on 404 (defense in depth): after resolving a name, if the exact-case fetch 404s, retry with the correct-cased name from a refreshed list.

[spacewander]

LGTM. Before I could merge it, could you update https://github.com/tj/git-extras/blob/main/Commands.md#git-ignore-io too?

[vjymisal0]

Thanks @spacewander! I updated Commands.md to reference the GitHub gitignore templates and corrected the git ignore-io vim example to use the Global/Vim template URL and current template content. Pushed as cb859c0 with DCO sign-off; git diff --check passes.

[vjymisal0]

Thanks @spacewander for the detailed review. The branch now uses the recursive GitHub tree endpoint, includes Global templates, refreshes invalid/legacy caches safely, preserves the cache between invocations, handles case-insensitive template lookup and 404 failures, and updates the generated documentation examples. I verified the branch is clean and pushed.