fish: add descriptions to fish shell completions (#9551)

Add descriptions to fish shell completions 

Claude Code used to understand the codebase and reason through the edge
cases (several iterations)

- Using first sentence from the Config to add description for each
config, even if sentence spans few lines
- Several options can share the same description, code doesn't duplicate
description, see screenshot in the posted issue thread below

Fixes [#9531](https://github.com/ghostty-org/ghostty/issues/9531)

build.zig

@@ -55,7 +55,7 @@ pub fn build(b: *std.Build) !void {
     );
 
     // Ghostty resources like terminfo, shell integration, themes, etc.
-    const resources = try buildpkg.GhosttyResources.init(b, &config);
+    const resources = try buildpkg.GhosttyResources.init(b, &config, &deps);
     const i18n = if (config.i18n) try buildpkg.GhosttyI18n.init(b, &config) else null;
 
     // Ghostty executable, the actual runnable Ghostty program.

src/build/GhosttyResources.zig

@@ -6,10 +6,11 @@ const assert = std.debug.assert;
 const buildpkg = @import("main.zig");
 const Config = @import("Config.zig");
 const RunStep = std.Build.Step.Run;
+const SharedDeps = @import("SharedDeps.zig");
 
 steps: []*std.Build.Step,
 
-pub fn init(b: *std.Build, cfg: *const Config) !GhosttyResources {
+pub fn init(b: *std.Build, cfg: *const Config, deps: *const SharedDeps) !GhosttyResources {
     var steps: std.ArrayList(*std.Build.Step) = .empty;
     errdefer steps.deinit(b.allocator);
 
@@ -26,6 +27,8 @@ pub fn init(b: *std.Build, cfg: *const Config) !GhosttyResources {
     });
     build_data_exe.linkLibC();
 
+    deps.help_strings.addImport(build_data_exe);
+
     // Terminfo
     terminfo: {
         const os_tag = cfg.target.result.os.tag;

src/extra/fish.zig

@@ -3,6 +3,7 @@ const std = @import("std");
 
 const Config = @import("../config/Config.zig");
 const Action = @import("../cli.zig").ghostty.Action;
+const help_strings = @import("help_strings");
 
 /// A fish completions configuration that contains all the available commands
 /// and options.
@@ -81,6 +82,15 @@ fn writeCompletions(writer: *std.Io.Writer) !void {
                 else => {},
             }
         }
+
+        if (@hasDecl(help_strings.Config, field.name)) {
+            const help = @field(help_strings.Config, field.name);
+            const desc = getDescription(help);
+            try writer.writeAll(" -d \"");
+            try writer.writeAll(desc);
+            try writer.writeAll("\"");
+        }
+
         try writer.writeAll("\n");
     }
 
@@ -143,3 +153,54 @@ fn writeCompletions(writer: *std.Io.Writer) !void {
         }
     }
 }
+
+fn getDescription(comptime help: []const u8) []const u8 {
+    var out: [help.len * 2]u8 = undefined;
+    var len: usize = 0;
+    var prev_was_space = false;
+
+    for (help, 0..) |c, i| {
+        switch (c) {
+            '.' => {
+                out[len] = '.';
+                len += 1;
+
+                if (i + 1 >= help.len) break;
+                const next = help[i + 1];
+                if (next == ' ' or next == '\n') break;
+            },
+            '\n' => {
+                if (!prev_was_space and len > 0) {
+                    out[len] = ' ';
+                    len += 1;
+                    prev_was_space = true;
+                }
+            },
+            '"' => {
+                out[len] = '\\';
+                out[len + 1] = '"';
+                len += 2;
+                prev_was_space = false;
+            },
+            else => {
+                out[len] = c;
+                len += 1;
+                prev_was_space = (c == ' ');
+            },
+        }
+    }
+
+    return out[0..len];
+}
+
+test "getDescription" {
+    const testing = std.testing;
+
+    const input = "First sentence with \"quotes\"\nand newlines. Second sentence.";
+    const expected = "First sentence with \\\"quotes\\\" and newlines.";
+
+    comptime {
+        const result = getDescription(input);
+        try testing.expectEqualStrings(expected, result);
+    }
+}