ripgrep: add --no-ignore-global flag

This commit adds a new --no-ignore-global flag that permits disabling
the use of global gitignore filtering. Global gitignores are generally
found in `$HOME/.config/git/ignore`, but its location can be configured
via git's `core.excludesFile` option.

Closes #934

4 files changed, 44 insertions, 7 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index d7afff46..987547aa 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -47,9 +47,12 @@ Feature enhancements:
 * [FEATURE #924](https://github.com/BurntSushi/ripgrep/issues/924):
   `termcolor` has moved to its own repository:
   https://github.com/BurntSushi/termcolor
+* [FEATURE #934](https://github.com/BurntSushi/ripgrep/issues/934):
+  Add a new flag, `--no-ignore-global`, that permits disabling global
+  gitignores.
 * [FEATURE #967](https://github.com/BurntSushi/ripgrep/issues/967):
-  Rename `--maxdepth` to `--max-depth` for consistency. We retain `--maxdepth`
-  as a synonym for backwards compatibility.
+  Rename `--maxdepth` to `--max-depth` for consistency. Keep `--maxdepth` for
+  backwards compatibility.
 * [FEATURE #978](https://github.com/BurntSushi/ripgrep/issues/978):
   Add a `--pre` option to filter inputs with an arbitrary program.
 * [FEATURE fca9709d](https://github.com/BurntSushi/ripgrep/commit/fca9709d):
@@ -84,8 +87,8 @@ Bug fixes:
 * [BUG #934](https://github.com/BurntSushi/ripgrep/issues/934):
   Don't respect gitignore files when searching outside git repositories.
 * [BUG #948](https://github.com/BurntSushi/ripgrep/issues/948):
-  ripgrep now uses an exit code of 2 to indicate an error, and uses an exit
-  code of 1 to indicate that no matches were found.
+  Use exit code 2 to indicate error, and use exit code 1 to indicate no
+  matches.
 * [BUG #951](https://github.com/BurntSushi/ripgrep/issues/951):
   Add stdin example to ripgrep usage documentation.
 * [BUG #955](https://github.com/BurntSushi/ripgrep/issues/955):
diff --git a/complete/_rg b/complete/_rg
index b943484d..573467bf 100644
--- a/complete/_rg
+++ b/complete/_rg
@@ -96,8 +96,12 @@ _rg() {
     $no"--no-hidden[don't search hidden files and directories]"
 
     + '(ignore)' # Ignore-file options
-    "(--no-ignore-parent --no-ignore-vcs)--no-ignore[don't respect ignore files]"
-    $no'(--ignore-parent --ignore-vcs)--ignore[respect ignore files]'
+    "(--no-ignore-global --no-ignore-parent --no-ignore-vcs)--no-ignore[don't respect ignore files]"
+    $no'(--ignore-global --ignore-parent --ignore-vcs)--ignore[respect ignore files]'
+
+    + '(ignore-global)' # Global ignore-file options
+    "--no-ignore-global[don't respect global ignore files]"
+    $no'--ignore-global[respect global ignore files]'
 
     + '(ignore-parent)' # Parent ignore-file options
     "--no-ignore-parent[don't respect ignore files in parent directories]"
diff --git a/src/app.rs b/src/app.rs
index 402bef5e..4bdf5bf4 100644
--- a/src/app.rs
+++ b/src/app.rs
@@ -527,6 +527,7 @@ pub fn all_args_and_flags() -> Vec<RGArg> {
     flag_mmap(&mut args);
     flag_no_config(&mut args);
     flag_no_ignore(&mut args);
+    flag_no_ignore_global(&mut args);
     flag_no_ignore_messages(&mut args);
     flag_no_ignore_parent(&mut args);
     flag_no_ignore_vcs(&mut args);
@@ -1230,6 +1231,26 @@ This flag can be disabled with the --ignore flag.
     args.push(arg);
 }
 
+fn flag_no_ignore_global(args: &mut Vec<RGArg>) {
+    const SHORT: &str = "Don't respect global ignore files.";
+    const LONG: &str = long!("\
+Don't respect ignore files that come from \"global\" sources such as git's
+`core.excludesFile` configuration option (which defaults to
+`$HOME/.config/git/ignore).
+
+This flag can be disabled with the --ignore-global flag.
+");
+    let arg = RGArg::switch("no-ignore-global")
+        .help(SHORT).long_help(LONG)
+        .overrides("ignore-global");
+    args.push(arg);
+
+    let arg = RGArg::switch("ignore-global")
+        .hidden()
+        .overrides("no-ignore-global");
+    args.push(arg);
+}
+
 fn flag_no_ignore_messages(args: &mut Vec<RGArg>) {
     const SHORT: &str = "Suppress gitignore parse error messages.";
     const LONG: &str = long!("\
diff --git a/src/args.rs b/src/args.rs
index 7100fc5c..1d7d1a8e 100644
--- a/src/args.rs
+++ b/src/args.rs
@@ -62,6 +62,7 @@ pub struct Args {
     max_filesize: Option<u64>,
     mmap: bool,
     no_ignore: bool,
+    no_ignore_global: bool,
     no_ignore_messages: bool,
     no_ignore_parent: bool,
     no_ignore_vcs: bool,
@@ -351,7 +352,9 @@ impl Args {
         wd.max_filesize(self.max_filesize);
         wd.overrides(self.glob_overrides.clone());
         wd.types(self.types.clone());
-        wd.git_global(!self.no_ignore && !self.no_ignore_vcs);
+        wd.git_global(
+            !self.no_ignore && !self.no_ignore_vcs && !self.no_ignore_global
+        );
         wd.git_ignore(!self.no_ignore && !self.no_ignore_vcs);
         wd.git_exclude(!self.no_ignore && !self.no_ignore_vcs);
         wd.ignore(!self.no_ignore);
@@ -413,6 +416,7 @@ impl<'a> ArgMatches<'a> {
             max_filesize: self.max_filesize()?,
             mmap: mmap,
             no_ignore: self.no_ignore(),
+            no_ignore_global: self.no_ignore_global(),
             no_ignore_messages: self.is_present("no-ignore-messages"),
             no_ignore_parent: self.no_ignore_parent(),
             no_ignore_vcs: self.no_ignore_vcs(),
@@ -1019,6 +1023,11 @@ impl<'a> ArgMatches<'a> {
         || self.occurrences_of("unrestricted") >= 1
     }
 
+    /// Returns true if global ignore files should be ignored.
+    fn no_ignore_global(&self) -> bool {
+        self.is_present("no-ignore-global") || self.no_ignore()
+    }
+
     /// Returns true if parent ignore files should be ignored.
     fn no_ignore_parent(&self) -> bool {
         self.is_present("no-ignore-parent") || self.no_ignore()