From d4b532ed5bfd15888c82f4c0a0d63383276bc094 Mon Sep 17 00:00:00 2001
From: Sebastian Pipping <sebastian@pipping.org>
Date: Wed, 15 Oct 2025 21:31:36 +0200
Subject: [PATCH] Make external diff command work again

.. by fixing SHA1 inspection in method copyFileToDiffIfNeeded
where any SHA1 matched regex pattern "0*".

That led the external diff feature to always compare the working
directory state of a file against itself rather than comparing
the version from a given commit against the version from the commit'
parent.

Regression from commit 1cb9acfa385e81cb9249e444603d7eff5be64c92
---
 src/mainimpl.cpp | 4 +---
 src/mainimpl.h   | 1 -
 2 files changed, 1 insertion(+), 4 deletions(-)

diff --git a/src/mainimpl.cpp b/src/mainimpl.cpp
index e88de1a..94855a4 100644
--- a/src/mainimpl.cpp
+++ b/src/mainimpl.cpp
@@ -291,10 +291,8 @@ void MainImpl::ActExternalDiff_activated() {
 	}
 }
 
-const QRegularExpression MainImpl::emptySha("0*");
-
 QString MainImpl::copyFileToDiffIfNeeded(QStringList* filenames, QString sha) {
-	if (emptySha.match(sha).hasMatch())
+	if (sha == QGit::ZERO_SHA)
 	{
 		return QString(curDir + "/" + rv->st.fileName());
 	}
diff --git a/src/mainimpl.h b/src/mainimpl.h
index 77a44aa..2d0afb7 100644
--- a/src/mainimpl.h
+++ b/src/mainimpl.h
@@ -187,7 +187,6 @@ protected slots:
 	QString textToFind;
 	QRegularExpression shortLogRE;
 	QRegularExpression longLogRE;
-	static const QRegularExpression emptySha;
 	QMap<QString, QVariant> revision_variables; // variables used in generic input dialogs
 	bool setRepositoryBusy;