From fa82b5c1ebbe56555065d6a3dad121ccbc22f0d4 Mon Sep 17 00:00:00 2001
From: Alexander Zhirov <azhirov@uveon.ru>
Date: Sat, 7 Jun 2025 18:32:45 +0300
Subject: [PATCH] =?UTF-8?q?=D0=94=D0=BE=D0=B1=D0=B0=D0=B2=D0=BB=D0=B5?=
 =?UTF-8?q?=D0=BD=20=D1=84=D0=BB=D0=B0=D0=B3=20--snapshot=20=D0=B4=D0=BB?=
 =?UTF-8?q?=D1=8F=20=D0=BA=D0=BE=D0=BC=D0=B0=D0=BD=D0=B4=D1=8B=20diff=20?=
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---
 source/app.d            | 14 ++++++++++++--
 source/snag/core/core.d | 41 +++++++++++++++++++++++++++++++++--------
 2 files changed, 45 insertions(+), 10 deletions(-)

diff --git a/source/app.d b/source/app.d
index d952688..8289191 100644
--- a/source/app.d
+++ b/source/app.d
@@ -39,7 +39,15 @@ int main(string[] args)
 			)
 		)
 		.add(new Command("status", "Checking the status of tracked files"))
-		.add(new Command("diff", "Show changed data"))
+		.add(new Command("diff", "Show changed data")
+			.add(new Option("s", "snapshot", "Specify snapshot hash")
+				.optional
+				.validateEachWith(
+					opt => opt.isValidHash,
+					"must contain snapshot hash provided"
+				)
+			)
+		)
 		.add(new Command("size", "Size of snapshots"))
 		.add(new Command("import", "Import snapshot from a tar.gz archive")
 			.add(new Argument("archive", "The path to the tar.gz archive file").required)
@@ -167,7 +175,9 @@ int main(string[] args)
 				snag.initialize(init.flag("force"))
 			)
 			.on("diff", diff =>
-				snag.diff()
+				snag.diff(
+					diff.option("snapshot", "")
+				)
 			)
 			.on("size", size =>
 				snag.size()
diff --git a/source/snag/core/core.d b/source/snag/core/core.d
index 4196481..0f97fbe 100644
--- a/source/snag/core/core.d
+++ b/source/snag/core/core.d
@@ -292,16 +292,41 @@ class Snag {
 		writeln("Backup was restored successfully: ", hash);
 	}
 
-	void diff() {
-		auto result = git(
-			["diff"],
-			"Failed to retrieve changes"
-		);
-		if (result.output.length) {
-			result.output.write;
+	void diff(string hash) {
+		string[] result;
+		if (hash.length) {
+			git(
+				["rev-parse", hash],
+				"This snapshot is not available in the archive"
+			);
+			result = git(
+				["show", hash, "--name-only", "--pretty="],
+				"Failed to retrieve snapshot information"
+			).output.split('\n').filter!(p => !p.empty).array;
+		} else {
+			result = git(
+				["diff", "--name-only"],
+				"Failed to retrieve changes"
+			).output.split('\n').filter!(p => !p.empty).array;
+		}
+		if (!result.length) {
+			writeln("No changes at the moment");
 			return;
 		}
-		writeln("No changes at the moment");
+		if (hash.length)
+			result.each!(e =>
+				git(
+					["show", "--pretty=", hash, "--", e],
+					"Failed to retrieve file information"
+				).output.write
+			);
+		else
+			result.each!(e =>
+				git(
+					["diff", e],
+					"Failed to retrieve file information"
+				).output.write
+			);
 	}
 
 	void exportSnapshot(string path, string hash) {