Remove --missing-as-empty from argument parsing and man page

Fixes #802

CHANGELOG.md

@@ -1,5 +1,10 @@
 ## 0.63 (unreleased)
 
+### Command Line Interface
+
+Difftastic no longer accepts the `--missing-as-empty`. This has had no
+effect since 0.46.
+
 ### Parsing
 
 File detection now supports Windows-1252 encoded test (an extension of

difft.1

@@ -78,10 +78,6 @@ Don\[cq]t consider comments when diffing.
 Print the all the languages supported by difftastic, along with their
 extensions.
 .TP
-\f[B]\-\-missing\-as\-empty\f[R]
-Treat paths that don\[cq]t exist as equivalent to an empty file.
-Only applies when diffing files, not directories.
-.TP
 \f[B]\-\-override\f[R] \f[I]GLOB:NAME\f[R]
 Associate this glob pattern with this language, overriding normal
 language detection.

difft.1.md

@@ -85,11 +85,6 @@ OPTIONS
 
 : Print the all the languages supported by difftastic, along with their extensions.
 
-**\-\-missing-as-empty**
-
-: Treat paths that don't exist as equivalent to an empty file. Only applies when diffing
-  files, not directories.
-
 **\-\-override** _GLOB:NAME_
 
 : Associate this glob pattern with this language, overriding normal language detection.

src/options.rs

@@ -249,10 +249,6 @@ json: Output the results as a machine-readable JSON array with an element per fi
                 .env("DFT_SKIP_UNCHANGED")
                 .help("Don't display anything if a file is unchanged.")
         )
-        .arg(
-            Arg::new("missing-as-empty").long("missing-as-empty")
-                .help("Treat paths that don't exist as equivalent to an empty file. Only applies when diffing files, not directories.")
-        )
         .arg(
             Arg::new("override").long("override")
                 .value_name("GLOB:NAME")