added GG_GIT_ALL behavior

README.md

@@ -26,13 +26,17 @@ It is intentionally narrow:
   skipped. A literal match that occurs *before* the first NUL in an
   otherwise-text file is still reported.
 - **Recursive by default.** Given a directory it walks the whole tree.
+- **Git-aware by default.** When walking a tree, `gg` honours every `.gitignore`
+  it encounters and always skips `.git` directories — just like `git` and `rg`.
+  Set `GG_GIT_ALL=1` to search everything instead (equivalent to `rg
+  --no-ignore`).
 - **Self-contained.** No third-party libraries, no shelling out to other
   programs. Just `libc` + `libpthread`.
 
 `gg` was built to be a clean, readable reference implementation that is also
 fast: on a 16 GB / ~209 000-file tree it completes the equivalent of
 `rg --no-ignore --hidden -l` in roughly **0.4 s**, about **1.5× faster than
-`rg`** on the same machine and query, using only portable POSIX interfaces.
+`rg`** on the same machine and query, using only portable POSIX interfaces. (With `GG_GIT_ALL` unset, the equivalent is `rg --hidden -l`.)
 
 ## Installation
 
@@ -113,8 +117,10 @@ gg "def main" src/main.py
 
 - **Symlinks are not followed.** Symbolic links to files or directories are
   skipped, which prevents infinite loops on symlink cycles.
-- **Hidden files and directories are searched.** Unlike `rg`'s default, `gg`
-  does not consult `.gitignore` or skip hidden paths.
+- **Hidden files and directories are searched.** `gg` does not skip hidden
+  paths. It *does* consult `.gitignore` files and skips `.git` directories by
+  default; set `GG_GIT_ALL=1` to disable that and search everything (including
+  ignored and `.git` paths).
 - **Binary files are skipped.** A file containing a NUL byte is never reported,
   even if it also contains the search term (except when the match occurs before
   the first NUL, in which case it is reported — see FAQ).
@@ -214,8 +220,20 @@ against symlink cycles and avoids double-counting.
 
 ### Does it respect `.gitignore`?
 
-No. `gg` searches everything it can read, including hidden files and directories.
-This is why its results match `rg --no-ignore --hidden`.
+Yes, by default. `gg` reads every `.gitignore` found while walking and skips
+matching files and directories, and it always skips `.git` directories — the
+same rules `git` itself uses (including `!` negation, `**` globs, and
+trailing-`/` directory-only patterns). Hidden files and directories are still
+searched; only `.gitignore`-matched paths and `.git` are excluded.
+
+To search everything — ignored files, `.git`, the lot — set the `GG_GIT_ALL`
+environment variable (to any value) before running `gg`:
+
+```sh
+GG_GIT_ALL=1 gg "needle" .
+```
+
+With `GG_GIT_ALL` set, `gg`'s results match `rg --no-ignore --hidden`.
 
 ### Why not `mmap` the files?