[gimp] Change logic to detect .git directory on repositories (or file on submodules)

[Jehan <jehanp src gnome org>]

commit e4c7fc233493b2c0b5a4d9b73755c0390bfa08c7
Author: Salamandar <felix piedallu me>
Date:   Thu Nov 14 14:14:53 2019 +0000

    Change logic to detect .git directory on repositories (or file on submodules)

 meson.build | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/meson.build b/meson.build
index 2930751ce3..c11afbedc8 100644
--- a/meson.build
+++ b/meson.build
@@ -17,8 +17,8 @@ warnings = []
 
 # git-version.h is already present and not generated if dist tarball
 is_dist_tarball = run_command('python', '-c',
-  'import sys,os; sys.exit(0 if os.path.exists("git-version.h") else 1)'
-).returncode() == 0
+  'import sys,os; sys.exit(0 if os.path.exists(".git") else 1)'
+).returncode() == 1
 
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 # Project info