populate: refer to flakes as git+file: only with a usable .git

Writing the lock file of a git+file: flake, Nix runs Git, with the
repository's configuration and hooks, which may run commands.  A .git
in a source's directory can come from anywhere, e.g. one planted in a
materialized flake, or one a file source keeps.  So drawing inputs
refers to a flake as git+file: only if git_problems finds nothing wrong
with its .git directory, the way git sources check their work trees,
and else as path:.

lock-foreign-git plants a .git in a materialized flake and in a file
source that keeps it, whose configuration names an fsmonitor command.

1 files changed, 4 insertions, 2 deletions

diff --git a/pkgs/populate/src/flake.rs b/pkgs/populate/src/flake.rs
index 26373d4..ded7692 100644
--- a/pkgs/populate/src/flake.rs
+++ b/pkgs/populate/src/flake.rs
@@ -228,8 +228,9 @@ impl<'a> Flakes<'a> {
             String::new()
         };
         format!(
-            "{}{}{require}{snippet}",
+            "{}{}{}{require}{snippet}",
             sh::prelude(),
+            sh::GIT_PROBLEMS,
             sh::draw::DEFINITIONS
         )
     }
@@ -270,7 +271,8 @@ impl<'a> Flakes<'a> {
             .collect())
     }
 
-    /// The flake URL of the source named name, at resolved.
+    /// The flake URL of the source named name, at resolved: git+file: if
+    /// it has a .git directory populate can use, else path:.
     fn flake_url(name: &str, resolved: &Resolved) -> Result<String> {
         if !resolved.dir {
             return Err(Failure::Message(format!(