Prevent fork nightmare with PAGER=batcat (#2235)

* Added rsamuelklatchko's changes

* Added some comments and deleted redundant code

* Ran cargo fmt

* Update src/pager.rs

Co-authored-by: Martin Nordholts <enselic@gmail.com>

* Added bugfix to changelog

* src/pager.rs nitpick: arg0 -> s

I forgot to comment on this name so I figured I'd just push a commit to
take care of it.

Co-authored-by: Martin Nordholts <enselic@gmail.com>

CHANGELOG.md

@@ -6,6 +6,8 @@
 
 ## Bugfixes
 
+- Prevent fork nightmare with `PAGER=batcat`. See #2235 (@johnmatthiggins)
+
 ## Other
 
 - Relaxed glibc requirements on amd64, see #2106 and #2194 (@sharkdp)

src/pager.rs

@@ -40,15 +40,23 @@ impl PagerKind {
     fn from_bin(bin: &str) -> PagerKind {
         use std::path::Path;
 
-        match Path::new(bin)
-            .file_stem()
-            .map(|s| s.to_string_lossy())
-            .as_deref()
-        {
-            Some("bat") => PagerKind::Bat,
+        // Set to `less` by default on most Linux distros.
+        let pager_bin = Path::new(bin).file_stem();
+
+        // The name of the current running binary. Normally `bat` but sometimes
+        // `batcat` for compatibility reasons.
+        let current_bin = env::args_os().next();
+
+        // Check if the current running binary is set to be our pager.
+        let is_current_bin_pager = current_bin
+            .map(|s| Path::new(&s).file_stem() == pager_bin)
+            .unwrap_or(false);
+
+        match pager_bin.map(|s| s.to_string_lossy()).as_deref() {
             Some("less") => PagerKind::Less,
             Some("more") => PagerKind::More,
             Some("most") => PagerKind::Most,
+            _ if is_current_bin_pager => PagerKind::Bat,
             _ => PagerKind::Unknown,
         }
     }