argv: permit repeated flags

This commit builds on the previous argv refactor by being more principled
about how we declared our flags. In particular, we now require that every
clap argument is one of three things: a positional argument, a switch or
a flag that accepts exactly one value. The latter two are always permitted
to be repeated, and we modify the code that consumes a clap::ArgMatches to
always use the *last* value of an argument. (clap by default always uses
the first value of argument, if it has been repeated and is accessed via
one of the singleton accessors.)

Fixes #553

src/args.rs

@@ -3,7 +3,6 @@ use std::env;
 use std::ffi::OsStr;
 use std::fs;
 use std::io::{self, BufRead};
-use std::ops;
 use std::path::{Path, PathBuf};
 use std::sync::Arc;
 use std::sync::atomic::{AtomicBool, Ordering};
@@ -305,11 +304,6 @@ impl Args {
 /// several options/flags.
 struct ArgMatches<'a>(clap::ArgMatches<'a>);
 
-impl<'a> ops::Deref for ArgMatches<'a> {
-    type Target = clap::ArgMatches<'a>;
-    fn deref(&self) -> &clap::ArgMatches<'a> { &self.0 }
-}
-
 impl<'a> ArgMatches<'a> {
     /// Convert the result of parsing CLI arguments into ripgrep's
     /// configuration.
@@ -376,7 +370,7 @@ impl<'a> ArgMatches<'a> {
 
     /// Return all file paths that ripgrep should search.
     fn paths(&self) -> Vec<PathBuf> {
-        let mut paths: Vec<PathBuf> = match self.values_of_os("PATH") {
+        let mut paths: Vec<PathBuf> = match self.values_of_os("path") {
             None => vec![],
             Some(vals) => vals.map(|p| Path::new(p).to_path_buf()).collect(),
         };
@@ -385,7 +379,7 @@ impl<'a> ArgMatches<'a> {
         if self.is_present("file")
             || self.is_present("files")
             || self.is_present("regexp") {
-            if let Some(path) = self.value_of_os("PATTERN") {
+            if let Some(path) = self.value_of_os("pattern") {
                 paths.insert(0, Path::new(path).to_path_buf());
             }
         }
@@ -451,7 +445,7 @@ impl<'a> ArgMatches<'a> {
         match self.values_of_os("regexp") {
             None => {
                 if self.values_of_os("file").is_none() {
-                    if let Some(os_pat) = self.value_of_os("PATTERN") {
+                    if let Some(os_pat) = self.value_of_os("pattern") {
                         pats.push(self.os_str_pattern(os_pat)?);
                     }
                 }
@@ -645,7 +639,7 @@ impl<'a> ArgMatches<'a> {
 
     /// Returns the replacement string as UTF-8 bytes if it exists.
     fn replace(&self) -> Option<Vec<u8>> {
-        self.value_of_lossy("replace").map(|s| s.into_owned().into_bytes())
+        self.value_of_lossy("replace").map(|s| s.into_bytes())
     }
 
     /// Returns the unescaped context separator in UTF-8 bytes.
@@ -695,9 +689,9 @@ impl<'a> ArgMatches<'a> {
     /// Returns the user's color choice based on command line parameters and
     /// environment.
     fn color_choice(&self) -> termcolor::ColorChoice {
-        let preference = match self.0.value_of_lossy("color") {
+        let preference = match self.value_of_lossy("color") {
             None => "auto".to_string(),
-            Some(v) => v.into_owned(),
+            Some(v) => v,
         };
         if preference == "always" {
             termcolor::ColorChoice::Always
@@ -743,7 +737,7 @@ impl<'a> ArgMatches<'a> {
     /// A `None` encoding implies that the encoding should be automatically
     /// detected on a per-file basis.
     fn encoding(&self) -> Result<Option<&'static Encoding>> {
-        match self.0.value_of_lossy("encoding") {
+        match self.value_of_lossy("encoding") {
             None => Ok(None),
             Some(label) => {
                 if label == "auto" {
@@ -942,6 +936,35 @@ impl<'a> ArgMatches<'a> {
             Some(v) => v.parse().map(Some).map_err(From::from),
         }
     }
+
+    // The following methods mostly dispatch to the underlying clap methods
+    // directly. Methods that would otherwise get a single value will fetch
+    // all values and return the last one. (Clap returns the first one.) We
+    // only define the ones we need.
+
+    fn is_present(&self, name: &str) -> bool {
+        self.0.is_present(name)
+    }
+
+    fn occurrences_of(&self, name: &str) -> u64 {
+        self.0.occurrences_of(name)
+    }
+
+    fn value_of_lossy(&self, name: &str) -> Option<String> {
+        self.values_of_lossy(name).and_then(|mut vals| vals.pop())
+    }
+
+    fn values_of_lossy(&self, name: &str) -> Option<Vec<String>> {
+        self.0.values_of_lossy(name)
+    }
+
+    fn value_of_os(&'a self, name: &str) -> Option<&'a OsStr> {
+        self.values_of_os(name).and_then(|it| it.last())
+    }
+
+    fn values_of_os(&'a self, name: &str) -> Option<clap::OsValues<'a>> {
+        self.0.values_of_os(name)
+    }
 }
 
 fn pattern_to_str(s: &OsStr) -> Result<&str> {