[fractal] Make pre-commit hook work for non-terminal environments

[Alejandro Domínguez <aledomu src gnome org>]

commit 32ccb30d31dafb0b3fd7c42a43d6f469bf7f9c8c
Author: Kai A. Hiller <V02460 gmail com>
Date:   Mon Dec 14 19:06:48 2020 +0100

    Make pre-commit hook work for non-terminal environments

 hooks/pre-commit.hook | 7 +++++++
 1 file changed, 7 insertions(+)
---
diff --git a/hooks/pre-commit.hook b/hooks/pre-commit.hook
index a367c2c9..92db1337 100755
--- a/hooks/pre-commit.hook
+++ b/hooks/pre-commit.hook
@@ -19,6 +19,13 @@ install_rustfmt() {
 
 if ! which cargo &> /dev/null || ! cargo fmt --help &> /dev/null; then
     echo "Can't check Fractal's code style, because rustfmt could not be run."
+
+    if [ ! -t 1 ]; then
+        # No input is possible
+        echo "Performing commit."
+        exit 0
+    fi
+
     echo ""
     echo "y: Install rustfmt via rustup"
     echo "n: Don't install rustfmt and perform the commit"