Follow Makefile includes when completing make targets

[maxmilian]

Summary

Fixes warpdotdev/warp#11705. make Tab-completion only suggested targets defined directly in the top-level Makefile; targets pulled in through include directives were invisible (other terminals show them, since GNU make treats included files as one unified ruleset).

Root cause

The make list_targets generator (command-signatures/src/generators/make.rs) ran cat [Mm]akefile, which reads only the root Makefile and never follows include / -include / sinclude directives.

Fix

Replace the command with a single self-contained awk program that echoes the root Makefile and recurses into included files, with a seen set guarding against include cycles. Design choices:

• All parsing happens inside awk (not a shell loop), so behavior is identical across the user's shell — sh/bash/zsh differ in word-splitting and this sidesteps that entirely.
• Injection-safe: included paths are opened directly via getline < path, never interpolated into a shell command, so a malicious Makefile can't inject commands.
• Fallback: awk output is captured and only emitted on a clean exit; otherwise it falls back to the original cat [Mm]akefile. An include pointing at a real directory (an invalid Makefile that make itself rejects) aborts some awk builds with an i/o error — the fallback keeps top-level targets working instead of returning nothing.

The Rust post_process (target + ## description parsing) is unchanged.

Tests

Two end-to-end tests run the actual generator command via sh -c against temp projects:

• test_list_targets_command_follows_includes — targets split across a nested include + a missing optional -include; also asserts a ## description defined in an included file survives.
• test_list_targets_command_survives_directory_include — a directory include still succeeds and falls back to top-level targets.

cargo fmt --check, cargo clippy --all-targets --all-features -- -D warnings, and cargo test all pass locally (61 tests).

Scope / known limitations

Include paths that rely on globbing (include dir/*.mk) or make variables (include $(VAR)) are intentionally left unresolved — expanding them safely would require either a shell (injection risk) or evaluating the Makefile. Explicit file paths (the reported case and the common case) and arbitrarily nested includes are handled.