doc terminal-compatibility: document Unicode characters used in output

Not sure if this will be useful but the fact that we use very
few Unicode characters, suggests that we are insecure about
this. Having some kind of central and explicit listing might help
future decision-making.  Obviously, completions and translations use
more characters, but those are not as central.

doc_src/terminal-compatibility.rst

@@ -285,3 +285,13 @@ Or add this to your ``config.fish``::
         commandline -f repaint
         functions --erase GNU-screen-workaround
     end
+
+Unicode Codepoints
+------------------
+
+By default, fish outputs the following non-ASCII characters::
+
+    × ► ¶ ⏎ • ● … μ – ’ ‘ “ ” ← → ↑ ↓
+
+as well as control pictures (U+2400 through U+241F),
+and locale-specific ones in :ref:`translated strings <variables-locale>`.

share/completions/help.fish

@@ -378,6 +378,8 @@ function __fish_help_describe -a help_item
             return
         case terminal-compatibility#required-commands
             return
+        case terminal-compatibility#unicode-codepoints
+            return
         case tutorial
             echo (_ Tutorial)
         case tutorial#autoloading-functions

src/common.rs

@@ -1032,10 +1032,9 @@ pub fn shell_modes() -> MutexGuard<'static, libc::termios> {
     crate::reader::SHELL_MODES.lock().unwrap()
 }
 
-/// The character to use where the text has been truncated. Is an ellipsis on unicode system and a $
+/// The character to use where the text has been truncated.
-/// on other systems.
 pub fn get_ellipsis_char() -> char {
-    '\u{2026}'
+    '\u{2026}' // ('…')
 }
 
 /// The character or string to use where text has been truncated (ellipsis if possible, otherwise
@@ -1245,7 +1244,7 @@ macro_rules! LL {
         // neither of \u23CE and \u25CF can be displayed in the default fonts on Windows, though
         // they can be *encoded* just fine. Use alternative glyphs.
         OMITTED_NEWLINE_STR.store(LL!("\u{00b6}")); // "pilcrow"
-        OBFUSCATION_READ_CHAR.store(u32::from('\u{2022}'), Ordering::Relaxed); // "bullet"
+        OBFUSCATION_READ_CHAR.store(u32::from('\u{2022}'), Ordering::Relaxed); // "bullet" (•)
     } else if is_console_session() {
         OMITTED_NEWLINE_STR.store(LL!("^J"));
         OBFUSCATION_READ_CHAR.store(u32::from('*'), Ordering::Relaxed);
@@ -1253,7 +1252,7 @@ macro_rules! LL {
         OMITTED_NEWLINE_STR.store(LL!("\u{23CE}")); // "return symbol" (⏎)
         OBFUSCATION_READ_CHAR.store(
             u32::from(
-                '\u{25CF}', // "black circle"
+                '\u{25CF}', // "black circle" (●)
             ),
             Ordering::Relaxed,
         );

src/exec.rs

@@ -1389,7 +1389,7 @@ fn get_deferred_process(j: &Job) -> Option<usize> {
 }
 
 /// Given that we failed to execute process `failed_proc` in job `job`, mark that process and
-/// every subsequent process in the pipeline as aborted before launch.
+/// every subsequent process in the pipeline as aborted before launch.
 fn abort_pipeline_from(job: &Job, offset: usize) {
     for p in job.processes().iter().skip(offset) {
         p.mark_aborted_before_launch();