fix: executable path in hooks

On platforms, where soft-serve executable gets installed in a path that
is not the same throughout installation, or upgrades, hooks break. Some
examples of such a situation is when moving soft-serve repositories from
one OS to another OS, or on NixOS/Guix

This commit passes the path to the current executable as an environment
variable $SOFT_SERVE_EXE_PATH to the hooks.

To fix/update existing repository hooks:

  [/path/to/soft-serve/repos] $ grep -ERl \
   '^[^[:space:]]+soft-serve[^[:space:]]+' . | xargs sed -r -e \
   's,^([^[:space:]]*soft-serve[^[:space:]]*),"${SOFT_SERVE_EXE_PATH}",g' -i

pkg/config/config.go

@@ -151,7 +151,14 @@ type Config struct {
 
 // Environ returns the config as a list of environment variables.
 func (c *Config) Environ() []string {
-	envs := []string{}
+	ex, err := os.Executable()
+	if err != nil {
+		ex = "soft-serve"
+	}
+	ex = filepath.ToSlash(ex)
+	envs := []string{
+		fmt.Sprintf("SOFT_SERVE_EXE_PATH=%s", ex),
+	}
 	if c == nil {
 		return envs
 	}

pkg/hooks/gen.go

@@ -78,7 +78,7 @@ func GenerateHooks(_ context.Context, cfg *config.Config, repo string) error {
 			Hook       string
 			Args       string
 		}{
-			Executable: ex,
+			Executable: "\"${SOFT_SERVE_EXE_PATH}\"",
 			Hook:       hook,
 			Args:       args,
 		}); err != nil {