Implement e (execute) command

[PranavRJoshi]

Fixes #476.

Implements the standalone e command (a GNU extension). Supports the command with and without arguments.

Changes:

• Added the e command in compiler.rs/processor.rs, both forms (with argument, bare/pattern-space). Argument parsing reuses the same escape decoding and backslash continuation as a/c/i, as GNU sed's e argument follows the same syntax.
• Rejected under --posix and --sandbox at compile time.
• Fixed e and s///e to silently swallowing the child shell's stderr.
• Added 17 tests covering both command forms, addressing, ';' not separating the argument, escape decoding, backslash continuation, --posix/--sandbox rejection, and stderr surfacing on failure.

Irrelevant: fixed a typo found at delimited_parser.rs.

[codecov]

Codecov Report

❌ Patch coverage is 2.40000% with 122 lines in your changes missing coverage. Please review.
✅ Project coverage is 83.80%. Comparing base (e9792a8) to head (a3bc1ed).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/sed/compiler.rs	4.54%	63 Missing ⚠️
src/sed/processor.rs	0.00%	59 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #481      +/-   ##
==========================================
- Coverage   84.98%   83.80%   -1.19%     
==========================================
  Files          13       13              
  Lines        6760     6859      +99     
  Branches      378      388      +10     
==========================================
+ Hits         5745     5748       +3     
- Misses       1012     1108      +96     
  Partials        3        3              

Flag	Coverage Δ
macos_latest	84.61% <2.47%> (-1.18%)	⬇️
ubuntu_latest	84.67% <2.47%> (-1.16%)	⬇️
windows_latest	0.00% <0.00%> (ø)

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[PranavRJoshi]

Seems like CRLF issue on Windows. Will make those tests conditionally compile on UNIX only.

[dspinellis]

Thank you for the quick turnaround and thorough testing! I added a few improvement suggestions.

[PranavRJoshi]

Appreciate the thorough review. Will make the appropriate changes and commit them later.

[dspinellis]

I see some potential clashes with the highly relevant #487. Are you OK to delay the review a bit until we can land that so that we can ensure compatibility? In the meantime, please

• try to address the drop in code coverage (I thought it would be addressed by your integration tests) , and
• see why the GNU test suite results haven't changed. You can run the suite through util/run-gnu-testsuite.sh.

[github-actions]

GNU sed testsuite comparison:

Test results comparison:
  Current:   TOTAL: 65 / PASSED: 13 / FAILED: 42 / SKIPPED: 10
  Reference: TOTAL: 65 / PASSED: 12 / FAILED: 43 / SKIPPED: 10

Changes from main branch:
  TOTAL: +0
  PASSED: +1
  FAILED: -1

Test improvements (1):
  + eval

[PranavRJoshi]

I went through the scripts exercising e/s///e. One of them, eval.sh, required strict flag ordering of p and e, which has been added. The other three that didn't pass was:

• sandbox.sh: The rejection behavior is correct. But it fails on the format, i.e., our sed reports in the format <script argument N>:L:C: error: while GNU sed reports in the format -e expression #1, char N:.
• posix-mode-s.sh: same format issue as well as unimplemented \l\L\U\u\E escapes. s///e execution passes.
• execute-tests.sh: unimplemented W/T/F and big-number q. The e part passes.

[dspinellis]

All comments have been well-addressed and the changes have been rebased (thanks).