Add same file system functionality

This adds a `--same-file-system` CLI option that instructs the walker to
not cross file system boundaries.
Due to the fact that the corresponding option of the `ignore` crate's
`WalkBuilder` does not support platforms other than Unix and Windows,
the option does nothing on platforms other than those.
Resolves sharkdp#507

README.md

@@ -293,19 +293,20 @@ USAGE:
     fd [FLAGS/OPTIONS] [<pattern>] [<path>...]
 
 FLAGS:
-    -H, --hidden            Search hidden files and directories
-    -I, --no-ignore         Do not respect .(git|fd)ignore files
-        --no-ignore-vcs     Do not respect .gitignore files
-    -s, --case-sensitive    Case-sensitive search (default: smart case)
-    -i, --ignore-case       Case-insensitive search (default: smart case)
-    -g, --glob              Glob-based search (default: regular expression)
-    -F, --fixed-strings     Treat the pattern as a literal string
-    -a, --absolute-path     Show absolute instead of relative paths
-    -L, --follow            Follow symbolic links
-    -p, --full-path         Search full path (default: file-/dirname only)
-    -0, --print0            Separate results by the null character
-    -h, --help              Prints help information
-    -V, --version           Prints version information
+    -H, --hidden              Search hidden files and directories
+    -I, --no-ignore           Do not respect .(git|fd)ignore files
+        --no-ignore-vcs       Do not respect .gitignore files
+    -s, --case-sensitive      Case-sensitive search (default: smart case)
+    -i, --ignore-case         Case-insensitive search (default: smart case)
+    -g, --glob                Glob-based search (default: regular expression)
+    -F, --fixed-strings       Treat the pattern as a literal string
+    -a, --absolute-path       Show absolute instead of relative paths
+    -L, --follow              Follow symbolic links
+        --same-file-system    Don't cross file system boundaries (only Unix/Windows)
+    -p, --full-path           Search full path (default: file-/dirname only)
+    -0, --print0              Separate results by the null character
+    -h, --help                Prints help information
+    -V, --version             Prints version information
 
 OPTIONS:
     -d, --max-depth <depth>            Set maximum search depth (default: none)

src/app.rs

@@ -115,6 +115,7 @@ pub fn build_app() -> App<'static, 'static> {
                 .alias("dereference")
                 .overrides_with("follow"),
         )
+        .arg(arg("same-file-system").long("same-file-system"))
         .arg(
             arg("full-path")
                 .long("full-path")
@@ -321,6 +322,11 @@ fn usage() -> HashMap<&'static str, Help> {
         , "Follow symbolic links"
         , "By default, fd does not descend into symlinked directories. Using this flag, symbolic \
            links are also traversed.");
+    doc!(h, "same-file-system"
+        , "Don't cross file system boundaries (only Unix/Windows)"
+        , "By default, fd will traverse the file system tree as far as other options dictate. \
+           With this flag, fd ensures that it does not descend into a different file system than \
+           the one it started in. Does nothing if not on Unix or Windows.");
     doc!(h, "full-path"
         , "Search full path (default: file-/dirname only)"
         , "By default, the search pattern is only matched against the filename (or directory \

src/internal/opts.rs

@@ -28,6 +28,9 @@ pub struct FdOptions {
     /// Whether to follow symlinks or not.
     pub follow_links: bool,
 
+    /// Whether to limit the search to starting file system or not.
+    pub same_file_system: bool,
+
     /// Whether elements of output should be separated by a null character
     pub null_separator: bool,
 

src/main.rs

@@ -191,6 +191,7 @@ fn main() {
             || matches.is_present("rg-alias-hidden-ignore")
             || matches.is_present("no-ignore-vcs")),
         follow_links: matches.is_present("follow"),
+        same_file_system: matches.is_present("same-file-system"),
         null_separator: matches.is_present("null_separator"),
         max_depth: matches
             .value_of("depth")

src/walk.rs

@@ -78,6 +78,8 @@ pub fn scan(path_vec: &[PathBuf], pattern: Arc<Regex>, config: Arc<FdOptions>) -
         .git_exclude(config.read_vcsignore)
         .overrides(overrides)
         .follow_links(config.follow_links)
+        // Same file system is only supported on Unix and Windows platforms
+        .same_file_system(config.same_file_system && (cfg!(unix) || cfg!(windows)))
         .max_depth(config.max_depth);
 
     if config.read_fdignore {