fix(registry): only rewrite last pipe segment; prevent data corruption in pipes/redirects

[youbamj]

Summary

Fixes critical data corruption bugs where RTK incorrectly filters piped or redirected commands, breaking downstream tools and producing malformed output files.

Real Bugs Fixed

Bug 1: Large JSON truncated, breaks jq

$ rtk curl https://jsonplaceholder.typicode.com/posts | jq
jq: parse error: Unfinished string at EOF at line 14, column 0

Root cause: RTK filters curl output, truncating large JSON responses. The truncated data is piped to jq, which fails to parse incomplete JSON.

Bug 2: Git diff corrupted when redirected to file

Before (RTK-filtered patch - BROKEN):

README.md | 2 ++
 1 file changed, 2 insertions(+)

--- Changes ---

README.md
  @@ -2,6 +2,8 @@
  +Change
  +
   <p align="center">
     <strong>High-performance CLI proxy that reduces LLM token consumption by 60-90%</strong>
   </p>
  +2 -0

After this fix (real patch - CORRECT):

diff --git a/README.md b/README.md
index d91e21b..dabe2cd 100644
--- a/README.md
+++ b/README.md
@@ -2,6 +2,8 @@
   <img src="https://avatars.githubusercontent.com/u/258253854?v=4" alt="RTK - Rust Token Killer" width="500">
 </p>
 
+Change
+
 <p align="center">
   <strong>High-performance CLI proxy that reduces LLM token consumption by 60-90%</strong>
 </p>

Result: git apply /tmp/rtk-test.patch fails with "No valid patches in input" on the RTK version, but succeeds on the real version.

Algorithm

1. Find last | in entire command
2. Everything before last | → stays raw (intermediate pipe segments)
3. Everything after last | → normal rewrite rules:
   • Check for file redirect (>, >>, &>) → skip entirely
   • Check if supported → prepend rtk if yes
4. Input redirect < is fine (reading from file, output still to terminal)

Examples

Input	Output	Reason
git log | cat && git stash	git log | rtk cat && rtk git stash	Only last segments get rtk
cargo test 2>&1 | head > file	None	Redirected to file, skip
cat < file.txt	rtk read - < file.txt	Input redirect is OK
find . | xargs grep pattern	find . | xargs rtk grep pattern	xargs is transparent
curl ... | jq	None	Pipe chain stays raw

Changes

• src/discover/registry.rs (+198, -62 lines)
  • Refactored rewrite_compound() with last-pipe detection
  • Extracted rewrite_segments() helper
  • Added has_stdout_redirect() (checks >, >>, &> only)
  • Fixed < input redirect to not block rewrite
  • Added xargs to SHELL_PREFIX_BUILTINS
  • Added 14 new/updated tests

Testing

cargo test        # 2016 passed, 0 failed
cargo fmt --all   # clean
cargo clippy --all-targets  # clean

Breaking Change

This changes the behavior of rtk rewrite for piped commands. Previously all commands in a pipe got rtk prefix; now only the last segment does. This is the correct Unix behavior but may surprise users relying on the old (broken) behavior.