Add --path-separator flag.

This flag permits setting the path separator used for all file paths
printed by ripgrep in normal operation.

Fixes #275

doc/rg.1

@@ -186,7 +186,7 @@ One byte is equal to one column.
 .RS
 .RE
 .TP
-.B \-\-context\-separator \f[I]ARG\f[]
+.B \-\-context\-separator \f[I]SEPARATOR\f[]
 The string to use when separating non\-continuous context lines.
 Escape sequences may be used.
 [default: \-\-]
@@ -328,6 +328,16 @@ and \-\-files.
 .RS
 .RE
 .TP
+.B \-\-path\-separator \f[I]SEPARATOR\f[]
+The path separator to use when printing file paths.
+This defaults to your platform\[aq]s path separator, which is / on Unix
+and \\ on Windows.
+This flag is intended for overriding the default when the environment
+demands it (e.g., cygwin).
+A path separator is limited to a single byte.
+.RS
+.RE
+.TP
 .B \-p, \-\-pretty
 Alias for \-\-color=always \-\-heading \-n.
 .RS

doc/rg.1.md

@@ -128,7 +128,7 @@ Project home page: https://github.com/BurntSushi/ripgrep
   numbers for the first match on each line. Note that this doesn't try
   to account for Unicode. One byte is equal to one column.
 
---context-separator *ARG*
+--context-separator *SEPARATOR*
 : The string to use when separating non-continuous context lines. Escape
   sequences may be used. [default: --]
 
@@ -221,6 +221,12 @@ Project home page: https://github.com/BurntSushi/ripgrep
   a list of matching files such as with --count, --files-with-matches
   and --files.
 
+--path-separator *SEPARATOR*
+: The path separator to use when printing file paths. This defaults to your
+  platform's path separator, which is / on Unix and \\ on Windows. This flag is
+  intended for overriding the default when the environment demands it (e.g.,
+  cygwin). A path separator is limited to a single byte.
+
 -p, --pretty
 : Alias for --color=always --heading -n.