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feature: add AI-powered Git diff analysis for working tree and commit range comparison #2457

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feature: add AI-powered Git diff analysis for working tree and commit…
YuHaoLiaoTony Jun 18, 2026
5bf31b0
feat(AI): 新增 AI 差異分析串流輸出支援
YuHaoLiaoTony Jun 18, 2026
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364 changes: 364 additions & 0 deletions src/AI/AIDiffContextBuilder.cs
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using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Text;
using System.Threading.Tasks;

namespace SourceGit.AI
{
public class AIDiffContextBuilder
{
private const int MAX_CHAR_COUNT = 100_000;
private const int MAX_LINE_COUNT = 3_000;
private const int MAX_FILE_DIFF_CHARS = 20_000;

public async Task<AIDiffContextData> CollectWorkingTreeAsync(string repoPath)
{
var data = new AIDiffContextData
{
Scenario = DiffScenario.WorkingTree
};

var unstagedStat = await RunGitAsync(repoPath, "diff --stat");
var stagedStat = await RunGitAsync(repoPath, "diff --cached --stat");
data.UnstagedStatText = unstagedStat;
data.StagedStatText = stagedStat;
data.DiffStatText = MergeStat(stagedStat, unstagedStat);

data.UnstagedNameStatus = await RunGitAsync(repoPath, "diff --name-status");
data.StagedNameStatus = await RunGitAsync(repoPath, "diff --cached --name-status");
data.NameStatusText = MergeNameStatus(data.StagedNameStatus, data.UnstagedNameStatus);

var unstagedPatch = await RunGitAsync(repoPath, "diff --no-color --no-ext-diff --full-index --patch");
var stagedPatch = await RunGitAsync(repoPath, "diff --cached --no-color --no-ext-diff --full-index --patch");

var combined = CombinePatches(stagedPatch, unstagedPatch);
combined = RemoveBinaryAndLFSSections(combined, data.SkippedBinaryFiles);
combined = RemoveLargeFileSections(combined, data.SkippedLargeFiles);

if (combined.Length > MAX_CHAR_COUNT || CountLines(combined) > MAX_LINE_COUNT)
{
data.FullDiffText = string.Empty;
data.IsTruncated = true;
}
else
{
data.FullDiffText = combined;
}

ParseStatSummary(data);
return data;
}

public async Task<AIDiffContextData> CollectCommitRangeAsync(string repoPath, string fromSHA, string toSHA)
{
if (!IsValidSHA(fromSHA))
throw new ArgumentException($"Invalid from SHA: {fromSHA}");
if (!IsValidSHA(toSHA))
throw new ArgumentException($"Invalid to SHA: {toSHA}");

var data = new AIDiffContextData
{
Scenario = DiffScenario.CommitRange,
FromSHA = fromSHA,
ToSHA = toSHA
};

data.CommitLogText = await RunGitAsync(repoPath, $"log --pretty=format:\"%h %s\" {fromSHA}..{toSHA}");
data.DiffStatText = await RunGitAsync(repoPath, $"diff --stat {fromSHA} {toSHA}");
data.NameStatusText = await RunGitAsync(repoPath, $"diff --name-status {fromSHA} {toSHA}");

var patch = await RunGitAsync(repoPath, $"diff --no-color --no-ext-diff --full-index --patch {fromSHA} {toSHA}");
patch = RemoveBinaryAndLFSSections(patch, data.SkippedBinaryFiles);
patch = RemoveLargeFileSections(patch, data.SkippedLargeFiles);

if (patch.Length > MAX_CHAR_COUNT || CountLines(patch) > MAX_LINE_COUNT)
{
data.FullDiffText = string.Empty;
data.IsTruncated = true;
}
else
{
data.FullDiffText = patch;
}

ParseStatSummary(data);
return data;
}

public async Task<(string fromSHA, string toSHA)> ResolveCommitDirectionAsync(string repoPath, string shaA, string shaB)
{
if (!IsValidSHA(shaA) || !IsValidSHA(shaB))
return (shaA, shaB);

var exitA = await RunGitExitCodeAsync(repoPath, $"merge-base --is-ancestor {shaA} {shaB}");
if (exitA == 0)
return (shaA, shaB);

var exitB = await RunGitExitCodeAsync(repoPath, $"merge-base --is-ancestor {shaB} {shaA}");
if (exitB == 0)
return (shaB, shaA);

return (shaA, shaB);
}

private async Task<string> RunGitAsync(string repoPath, string args)
{
using var proc = new Process();
proc.StartInfo = new ProcessStartInfo
{
FileName = Native.OS.GitExecutable,
Arguments = $"--no-pager -c core.quotepath=off {args}",
WorkingDirectory = repoPath,
RedirectStandardOutput = true,
RedirectStandardError = true,
StandardOutputEncoding = Encoding.UTF8,
StandardErrorEncoding = Encoding.UTF8,
UseShellExecute = false,
CreateNoWindow = true,
};
proc.Start();
var output = await proc.StandardOutput.ReadToEndAsync();
var error = await proc.StandardError.ReadToEndAsync();
await proc.WaitForExitAsync();
if (proc.ExitCode != 0 && !string.IsNullOrEmpty(error))
return string.Empty;
return output ?? string.Empty;
}

private async Task<int> RunGitExitCodeAsync(string repoPath, string args)
{
using var proc = new Process();
proc.StartInfo = new ProcessStartInfo
{
FileName = Native.OS.GitExecutable,
Arguments = $"--no-pager {args}",
WorkingDirectory = repoPath,
RedirectStandardOutput = true,
RedirectStandardError = true,
UseShellExecute = false,
CreateNoWindow = true,
};
proc.Start();
await proc.WaitForExitAsync();
return proc.ExitCode;
}

private static bool IsValidSHA(string sha)
{
if (string.IsNullOrEmpty(sha))
return false;
if (sha.Length < 6 || sha.Length > 64)
return false;
foreach (var c in sha)
if (!char.IsAsciiHexDigit(c))
return false;
return true;
}

private static string MergeStat(string staged, string unstaged)
{
if (string.IsNullOrEmpty(staged) && string.IsNullOrEmpty(unstaged))
return string.Empty;
if (string.IsNullOrEmpty(staged))
return unstaged;
if (string.IsNullOrEmpty(unstaged))
return staged;
return staged.TrimEnd() + "\n" + unstaged.TrimEnd();
}

private static string MergeNameStatus(string staged, string unstaged)
{
if (string.IsNullOrEmpty(staged) && string.IsNullOrEmpty(unstaged))
return string.Empty;
if (string.IsNullOrEmpty(staged))
return unstaged;
if (string.IsNullOrEmpty(unstaged))
return staged;
return staged.TrimEnd() + "\n" + unstaged.TrimEnd();
}

private static string CombinePatches(string staged, string unstaged)
{
if (string.IsNullOrEmpty(staged) && string.IsNullOrEmpty(unstaged))
return string.Empty;
if (string.IsNullOrEmpty(staged))
return unstaged;
if (string.IsNullOrEmpty(unstaged))
return staged;

var builder = new StringBuilder();
builder.AppendLine("=== STAGED CHANGES ===");
builder.Append(staged.TrimEnd());
builder.AppendLine();
builder.AppendLine("=== UNSTAGED CHANGES ===");
builder.Append(unstaged.TrimEnd());
return builder.ToString();
}

private static string RemoveBinaryAndLFSSections(string patch, List<string> skipped)
{
if (string.IsNullOrEmpty(patch))
return patch;

var lines = patch.Split('\n');
var result = new List<string>();
var inBinary = false;
var inLFS = false;
var currentFile = string.Empty;

for (int i = 0; i < lines.Length; i++)
{
var line = lines[i];

if (line.StartsWith("diff --git ", StringComparison.Ordinal))
{
inBinary = false;
inLFS = false;

var parts = line.Split(' ');
if (parts.Length >= 3)
currentFile = parts[3].TrimStart("a/".ToCharArray());
else
currentFile = string.Empty;
}

if (line.StartsWith("Binary", StringComparison.Ordinal))
{
inBinary = true;
if (!string.IsNullOrEmpty(currentFile))
skipped.Add(currentFile);
continue;
}

if (line.Contains("version https://git-lfs.github.com/spec/", StringComparison.Ordinal))
{
inLFS = true;
if (!string.IsNullOrEmpty(currentFile) && !skipped.Contains(currentFile))
skipped.Add(currentFile);
continue;
}

if (inBinary || inLFS)
{
if (line.StartsWith("diff --git ", StringComparison.Ordinal))
{
inBinary = false;
inLFS = false;
result.Add(line);
}
continue;
}

result.Add(line);
}

return string.Join("\n", result);
}

private static string RemoveLargeFileSections(string patch, List<string> skipped)
{
if (string.IsNullOrEmpty(patch))
return patch;

var lines = patch.Split('\n');
var result = new List<string>();
var currentFile = string.Empty;
var sectionStart = -1;
var sectionChars = 0;

for (int i = 0; i < lines.Length; i++)
{
var line = lines[i];

if (line.StartsWith("diff --git ", StringComparison.Ordinal))
{
if (sectionStart >= 0 && sectionChars > MAX_FILE_DIFF_CHARS)
{
for (int j = sectionStart; j < i; j++)
{
if (result.Count > 0)
result.RemoveAt(result.Count - 1);
}
if (!string.IsNullOrEmpty(currentFile))
skipped.Add(currentFile);
}

var parts = line.Split(' ');
currentFile = parts.Length >= 4 ? parts[3].TrimStart("a/".ToCharArray()) : string.Empty;
sectionStart = result.Count;
sectionChars = 0;
result.Add(line);
continue;
}

result.Add(line);
sectionChars += line.Length + 1;

if (i == lines.Length - 1 && sectionStart >= 0 && sectionChars > MAX_FILE_DIFF_CHARS)
{
for (int j = sectionStart; j < result.Count; )
{
if (result.Count > 0)
result.RemoveAt(result.Count - 1);
}
if (!string.IsNullOrEmpty(currentFile))
skipped.Add(currentFile);
}
}

return string.Join("\n", result);
}

private static int CountLines(string text)
{
if (string.IsNullOrEmpty(text))
return 0;
var count = 1;
foreach (var c in text)
if (c == '\n')
count++;
return count;
}

private static void ParseStatSummary(AIDiffContextData data)
{
var text = data.DiffStatText;
if (string.IsNullOrEmpty(text))
return;

var lines = text.Split('\n', StringSplitOptions.RemoveEmptyEntries);
foreach (var line in lines)
{
if (line.Contains(" file changed", StringComparison.Ordinal) ||
line.Contains(" files changed", StringComparison.Ordinal))
{
var parts = line.Split(',');
foreach (var part in parts)
{
var trimmed = part.Trim();
if (trimmed.Contains(" file", StringComparison.Ordinal))
{
var numStr = trimmed.Split(' ')[0];
if (int.TryParse(numStr, out var files))
data.TotalFiles = files;
}
else if (trimmed.Contains(" insertion", StringComparison.Ordinal))
{
var numStr = trimmed.Split(' ')[0];
if (int.TryParse(numStr, out var ins))
data.TotalInsertions = ins;
}
else if (trimmed.Contains(" deletion", StringComparison.Ordinal))
{
var numStr = trimmed.Split(' ')[0];
if (int.TryParse(numStr, out var del))
data.TotalDeletions = del;
}
}
break;
}
}
}
}
}
30 changes: 30 additions & 0 deletions src/AI/AIDiffContextData.cs
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using System.Collections.Generic;

namespace SourceGit.AI
{
public enum DiffScenario { WorkingTree, CommitRange }

public class AIDiffContextData
{
public DiffScenario Scenario { get; set; }

public string DiffStatText { get; set; } = string.Empty;
public string NameStatusText { get; set; } = string.Empty;
public string FullDiffText { get; set; } = string.Empty;
public bool IsTruncated { get; set; }
public int TotalFiles { get; set; }
public int TotalInsertions { get; set; }
public int TotalDeletions { get; set; }
public List<string> SkippedBinaryFiles { get; set; } = [];
public List<string> SkippedLargeFiles { get; set; } = [];

public string FromSHA { get; set; } = string.Empty;
public string ToSHA { get; set; } = string.Empty;
public string CommitLogText { get; set; } = string.Empty;

public string StagedStatText { get; set; } = string.Empty;
public string UnstagedStatText { get; set; } = string.Empty;
public string StagedNameStatus { get; set; } = string.Empty;
public string UnstagedNameStatus { get; set; } = string.Empty;
}
}
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