feature(LFS): LFS diff and preview support

src/Git/Diff.cs

@@ -31,14 +31,6 @@ namespace SourceGit.Git {
             Both,
         }
 
-        /// <summary>
-        ///     Binary change.
-        /// </summary>
-        public class BinaryChange {
-            public long Size = 0;
-            public long PreSize = 0;
-        }
-
         /// <summary>
         ///     Block
         /// </summary>
@@ -63,9 +55,9 @@ namespace SourceGit.Git {
         }
 
         /// <summary>
-        ///     Diff result.
+        ///     Text file change.
         /// </summary>
-        public class Result {
+        public class TextChange {
             public bool IsValid = false;
             public bool IsBinary = false;
             public List<Block> Blocks = new List<Block>();
@@ -119,14 +111,31 @@ namespace SourceGit.Git {
             }
         }
 
+        /// <summary>
+        ///     Binary change.
+        /// </summary>
+        public class BinaryChange {
+            public long Size = 0;
+            public long PreSize = 0;
+        }
+
+        /// <summary>
+        ///     Change for LFS object information.
+        /// </summary>
+        public class LFSChange {
+            public LFSObject Old;
+            public LFSObject New;
+            public bool IsValid => Old != null || New != null;
+        }
+
         /// <summary>
         ///     Run diff process.
         /// </summary>
         /// <param name="repo"></param>
         /// <param name="args"></param>
         /// <returns></returns>
-        public static Result Run(Repository repo, string args) {
-            var rs = new Result();
+        public static TextChange GetTextChange(Repository repo, string args) {
+            var rs = new TextChange();
             var current = new Block();
             var left = 0;
             var right = 0;
@@ -259,5 +268,37 @@ namespace SourceGit.Git {
 
             return change;
         }
+
+        /// <summary>
+        ///     Get LFS object changes.
+        /// </summary>
+        /// <param name="repo"></param>
+        /// <param name="args"></param>
+        /// <returns></returns>
+        public static LFSChange GetLFSChange(Repository repo, string args) {
+            var rc = new LFSChange();
+
+            repo.RunCommand($"diff --ignore-cr-at-eol {args}", line => {
+                if (line[0] == '-') {
+                    if (rc.Old == null) rc.Old = new LFSObject();
+                    line = line.Substring(1);
+                    if (line.StartsWith("oid sha256:")) {
+                        rc.Old.OID = line.Substring(11);
+                    } else if (line.StartsWith("size ")) {
+                        rc.Old.Size = int.Parse(line.Substring(5));
+                    }
+                } else if (line[0] == '+') {
+                    if (rc.New == null) rc.New = new LFSObject();
+                    line = line.Substring(1);
+                    if (line.StartsWith("oid sha256:")) {
+                        rc.New.OID = line.Substring(11);
+                    } else if (line.StartsWith("size ")) {
+                        rc.New.Size = int.Parse(line.Substring(5));
+                    }
+                }
+            });
+
+            return rc;
+        }
     }
 }

src/Git/LFS.cs

@@ -0,0 +1,18 @@
+namespace SourceGit.Git {
+    
+    /// <summary>
+    ///    Object filtered by LFS 
+    /// </summary>
+    public class LFSObject {
+
+        /// <summary>
+        ///     Object id
+        /// </summary>
+        public string OID { get; set; }
+
+        /// <summary>
+        ///     Object size.
+        /// </summary>
+        public long Size { get; set; }
+    }
+}

src/Git/Repository.cs

@@ -999,11 +999,46 @@ namespace SourceGit.Git {
         /// <returns></returns>
         public long GetFileSize(string sha, string path) {
             long size = 0;
+
             RunCommand($"cat-file -s {sha}:\"{path}\"", line => {
                 if (!long.TryParse(line, out size)) size = 0;
             });
+
             return size;
         }
+        
+        /// <summary>
+        ///     Detect if a file is managed by LFS.
+        /// </summary>
+        /// <param name="path">File path</param>
+        /// <returns></returns>
+        public bool IsLFSFiltered(string path) {
+            bool ok = false;
+            RunCommand($"check-attr -a -z \"{path}\"", line => {
+                ok = ok || line.Contains("filter\0lfs");
+            });
+            return ok;
+        }
+
+        /// <summary>
+        ///     Get LFS object information.
+        /// </summary>
+        /// <param name="sha"></param>
+        /// <param name="path"></param>
+        /// <returns></returns>
+        public LFSObject GetLFSObject(string sha, string path) {
+            LFSObject obj = new LFSObject();
+
+            RunCommand($"show {sha}:\"{path}\"", line => {
+                if (line.StartsWith("oid")) {
+                    obj.OID = line.Substring(3).Replace("sha256:", "").Trim();
+                } else if (line.StartsWith("size")) {
+                    obj.Size = int.Parse(line.Substring(4).Trim());
+                }                
+            });
+
+            return obj;
+        }
         #endregion
 
         #region METHOD_GITFLOW