build: fix cargo publish by symlinking cli/docs->docs

I think `cargo publish` will currently fail because of the
`include_str!()` in `cli/src/commands/help.rs` pointing to
`../../../docs/`, i.e. outside of the crate directory. This patch
attempts to fix that creating a `cli/docs` symlink to `docs` and makes
the `include_str!` use that symlink. I hope the symlink will be
resolved at `cargo publish` time so it also works in the published
crate.

Because symlinks don't work well on Windows, I updated `cli/build.rs`
to include the original path (the one pointing outside the crate) if
`cli/docs` is not a symlink, so the regular build still should work on
Windows (but `cargo publish` won't).

Thanks to Yuya for proposing this solution.

cli/Cargo.toml

@@ -18,6 +18,7 @@ include = [
     "/build.rs",
     "/examples/",
     "/src/",
+    "/docs/**",
     "/testing/",
     "/tests/",
     "!*.pending-snap",

cli/build.rs

@@ -37,6 +37,14 @@ fn main() {
     } else {
         println!("cargo:rustc-env=JJ_VERSION={version}");
     }
+
+    let docs_symlink_path = Path::new("docs");
+    println!("cargo:rerun-if-changed={}", docs_symlink_path.display());
+    if docs_symlink_path.join("index.md").exists() {
+        println!("cargo:rustc-env=JJ_DOCS_DIR=docs/");
+    } else {
+        println!("cargo:rustc-env=JJ_DOCS_DIR=../docs/");
+    }
 }
 
 fn get_git_hash() -> Option<String> {

cli/docs

@@ -0,0 +1 @@
+../docs

cli/src/commands/help.rs

@@ -98,12 +98,12 @@ const KEYWORDS: &[Keyword] = &[
     Keyword {
         name: "revsets",
         description: "A functional language for selecting a set of revision",
-        content: include_str!("../../../docs/revsets.md"),
+        content: include_str!(concat!("../../", env!("JJ_DOCS_DIR"), "revsets.md")),
     },
     Keyword {
         name: "tutorial",
         description: "Show a tutorial to get started with jj",
-        content: include_str!("../../../docs/tutorial.md"),
+        content: include_str!(concat!("../../", env!("JJ_DOCS_DIR"), "tutorial.md")),
     },
 ];