From 71a6c71ac18e343b2f484af8e8d0722428117d78 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Daniel=20H=C3=B6xtermann?= <daniel@hxtm.dev>
Date: Tue, 9 Sep 2025 12:12:20 +0200
Subject: [PATCH] feat(nixery): make default tag configurable

---
 README.md           |  1 +
 config/pkgsource.go | 10 +++++++---
 2 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/README.md b/README.md
index 40009b0..c337430 100644
--- a/README.md
+++ b/README.md
@@ -84,6 +84,7 @@ variables:
 * `NIXERY_CHANNEL`: The name of a Nix/NixOS channel to use for building
 * `NIXERY_PKGS_REPO`: URL of a git repository containing a package set (uses
   locally configured SSH/git credentials)
+* `NIXERY_DEFAULT_TAG`: rev/ref to use as the default for `latest`/empty
 * `NIXERY_PKGS_PATH`: A local filesystem path containing a Nix package set to
   use for building
 * `NIXERY_STORAGE_BACKEND`: The type of backend storage to use, currently
diff --git a/config/pkgsource.go b/config/pkgsource.go
index eb52cfc..5688593 100644
--- a/config/pkgsource.go
+++ b/config/pkgsource.go
@@ -49,10 +49,14 @@ func (g *GitSource) Render(tag string) (string, string) {
 		"url": g.repository,
 	}
 
-	// The 'git' source requires a tag to be present. If the user
-	// has not specified one, it is assumed that 'HEAD' should be used.
+	// If the user has not specified a non-default tag,
+	// use $NIXERY_DEFAULT_TAG or HEAD as the tag.
 	if tag == "latest" || tag == "" {
-		tag = "HEAD"
+		if default_tag := os.Getenv("NIXERY_DEFAULT_TAG"); default_tag != "" {
+			tag = default_tag
+		} else {
+			tag = "HEAD"
+		}
 	}
 
 	if commitRegex.MatchString(tag) {