feat(shell-integration): add automatic integration for Elvish

Fish automatic integration taken as an example.
Just like fish, Elvish checks `XDG_DATA_DIRS` for its modules.
Thus, Fish integration in zig is reused, and integration in
Elvish now removes `GHOSTTY_FISH_XDG_DIR` environment variable
on launch.

src/config/Config.zig

@@ -3414,6 +3414,7 @@ pub const ShellIntegration = enum {
     bash,
     fish,
     zsh,
+    elvish,
 };
 
 /// Shell integration features

src/shell-integration/README.md

@@ -19,9 +19,20 @@ its normal startup files, which becomes our script's responsibility (along with
 disabling POSIX mode).
 
 Bash shell integration can also be sourced manually from `bash/ghostty.bash`.
-
 ### Elvish
 
+For [Elvish](https://elv.sh), `$GHOSTTY_RESOURCES_DIR/src/shell-integration`
+contains an `./elvish/lib/ghostty-integration.elv` file.
+
+Elvish, on startup, searches for paths defined in `XDG_DATA_DIRS`
+variable for `./elvish/lib/*.elv` files and imports them. They are thus
+made available for use as modules by way of `use <filename>`.
+
+Ghostty launches Elvish, passing the environment with `XDG_DATA_DIRS`prepended
+with `$GHOSTTY_RESOURCES_DIR/src/shell-integration`. It contains
+`./elvish/lib/ghostty-integration.elv`. The user can then import it
+by `use ghostty-integration`, which will run the integration routines.
+
 The [Elvish](https://elv.sh) shell integration is supported by
 the community and is not officially supported by Ghostty. We distribute
 it for ease of access and use but do not provide support for it.
@@ -43,3 +54,4 @@ For `zsh`, Ghostty sets `ZDOTDIR` so that it loads our configuration
 from the `zsh` directory. The existing `ZDOTDIR` is retained so that
 after loading the Ghostty shell integration the normal Zsh loading
 sequence occurs.
+

src/shell-integration/elvish/lib/ghostty-integration.elv

@@ -1,6 +1,6 @@
 {
   fn restore-xdg-dirs {
-    var integration-dir = $E:GHOSTTY_FISH_XDG_DIR
+    var integration-dir = $E:GHOSTTY_INTEGRATION_DIR
     var xdg-dirs = [(str:split ':' $E:XDG_DATA_DIRS)]
     var len = (count $xdg-dirs)
 
@@ -27,9 +27,9 @@
     } else {
       set-env XDG_DATA_DIRS (str:join ':' $xdg-dirs)
     }
-    unset-env GHOSTTY_FISH_XDG_DIR
+    unset-env GHOSTTY_INTEGRATION_DIR
   }
-  if (and (has-env GHOSTTY_FISH_XDG_DIR) (has-env XDG_DATA_DIRS)) {
+  if (and (has-env GHOSTTY_INTEGRATION_DIR) (has-env XDG_DATA_DIRS)) {
     restore-xdg-dirs
   }
 }
@@ -117,4 +117,3 @@
     edit:add-var sudo~ $sudo-with-terminfo~
   }
 }
-

src/termio/shell_integration.zig

@@ -12,6 +12,7 @@ pub const Shell = enum {
     bash,
     fish,
     zsh,
+    elvish,
 };
 
 /// The result of setting up a shell integration.
@@ -47,6 +48,7 @@ pub fn setup(
         .bash => "bash",
         .fish => "fish",
         .zsh => "zsh",
+        .elvish => "elvish",
     } else exe: {
         // The command can include arguments. Look for the first space
         // and use the basename of the first part as the command's exe.
@@ -76,6 +78,14 @@ pub fn setup(
             };
         }
 
+        if (std.mem.eql(u8, "elvish", exe)) {
+            try setupElvish(alloc_arena, resource_dir, env);
+            break :shell .{
+                .shell = .elvish,
+                .command = command,
+            };
+        }
+
         if (std.mem.eql(u8, "zsh", exe)) {
             try setupZsh(resource_dir, env);
             break :shell .{
@@ -452,6 +462,18 @@ fn setupFish(
     }
 }
 
+/// Setup the Elvish automatic shell integration.
+/// This reuses integration primitives of Fish, as Elvish also
+/// loads config in XDG_DATA_DIRS (except it imports
+/// "./elvish/lib/*.elv" files).
+fn setupElvish(
+    alloc_arena: Allocator,
+    resource_dir: []const u8,
+    env: *EnvMap,
+) !void {
+    try setupFish(alloc_arena, resource_dir, env);
+}
+
 /// Setup the zsh automatic shell integration. This works by setting
 /// ZDOTDIR to our resources dir so that zsh will load our config. This
 /// config then loads the true user config.