xtask: Handle being in the right git dir without looking for ADOPTERS.md (#2077)

It turns out that things like `fedpkg local` break today because
they'll do a build directly from dist-git and our code gets
confused by this (because dist-git != upstream git). It doesn't
affect "production" Koji builds because I think for historical
reasons that doesn't mount the dist-git .git dir?

Anyways...make this work more nicely by looking for ADOPTERS.md
first and if we're already in the right dir, then we're done
and no need to look for git.

Signed-off-by: Colin Walters <walters@verbum.org>

Author: cgwalters

crates/xtask/src/xtask.rs

@@ -21,6 +21,8 @@ mod man;
 mod tmt;
 
 const NAME: &str = "bootc";
+/// File used to identify the bootc source tree toplevel.
+const TOPLEVEL_MARKER: &str = "ADOPTERS.md";
 const TAR_REPRODUCIBLE_OPTS: &[&str] = &[
     "--sort=name",
     "--owner=0",
@@ -201,9 +203,20 @@ fn main() {
     }
 }
 
+/// Check if we're in a bootc source tree by looking for [`TOPLEVEL_MARKER`].
+fn in_bootc_source_tree() -> Result<bool> {
+    Utf8Path::new(TOPLEVEL_MARKER)
+        .try_exists()
+        .context("Checking for toplevel")
+}
+
 fn try_main() -> Result<()> {
-    // Ensure our working directory is the toplevel (if we're in a git repo)
-    {
+    // Ensure our working directory is the bootc source toplevel.
+    // First check if we're already there (e.g. when invoked from extracted
+    // tarball during RPM build). Only try git if we're not already in the
+    // right place - this avoids issues when building inside a different
+    // git repository.
+    if !in_bootc_source_tree()? {
         if let Ok(toplevel_path) = Command::new("git")
             .args(["rev-parse", "--show-toplevel"])
             .output()
@@ -213,12 +226,9 @@ fn try_main() -> Result<()> {
                 std::env::set_current_dir(path.trim()).context("Changing to toplevel")?;
             }
         }
-        // Otherwise verify we're in the toplevel
-        if !Utf8Path::new("ADOPTERS.md")
-            .try_exists()
-            .context("Checking for toplevel")?
-        {
-            anyhow::bail!("Not in toplevel")
+        // Verify we're now in the toplevel
+        if !in_bootc_source_tree()? {
+            anyhow::bail!("Not in toplevel (no {TOPLEVEL_MARKER} found)")
         }
     }