diff --git a/docs/diff-tool.md b/docs/diff-tool.md
index 62717df3..3a9f3eac 100644
--- a/docs/diff-tool.md
+++ b/docs/diff-tool.md
@@ -53,6 +53,8 @@ This value can be changed:
Setting the `DiffEngine_MaxInstances` environment variable to the number of instances to launch.
+This value can also be set using [the DiffEngineTray options dialog](/docs/tray.md#max-instances-to-launch).
+
### Using code
@@ -71,7 +73,7 @@ By default, when a diff is opened, the temp file is on the left and the target f
This value can be changed by setting the `DiffEngine_TargetOnLeft` environment variable to `true`.
-This value can also be set using [the DiffEngineTray options dialog](https://github.com/VerifyTests/DiffEngine/blob/main/docs/tray.md#open-on-left).
+This value can also be set using [the DiffEngineTray options dialog](/docs/tray.md#open-on-left).
## Successful verification behavior
diff --git a/docs/mdsource/diff-tool.source.md b/docs/mdsource/diff-tool.source.md
index ee1261f1..29838fa5 100644
--- a/docs/mdsource/diff-tool.source.md
+++ b/docs/mdsource/diff-tool.source.md
@@ -46,6 +46,8 @@ This value can be changed:
Setting the `DiffEngine_MaxInstances` environment variable to the number of instances to launch.
+This value can also be set using [the DiffEngineTray options dialog](/docs/tray.md#max-instances-to-launch).
+
### Using code
@@ -58,7 +60,7 @@ By default, when a diff is opened, the temp file is on the left and the target f
This value can be changed by setting the `DiffEngine_TargetOnLeft` environment variable to `true`.
-This value can also be set using [the DiffEngineTray options dialog](https://github.com/VerifyTests/DiffEngine/blob/main/docs/tray.md#open-on-left).
+This value can also be set using [the DiffEngineTray options dialog](/docs/tray.md#open-on-left).
## Successful verification behavior
diff --git a/docs/mdsource/tray.source.md b/docs/mdsource/tray.source.md
index 8c6c613a..1ea270f5 100644
--- a/docs/mdsource/tray.source.md
+++ b/docs/mdsource/tray.source.md
@@ -69,6 +69,11 @@ Runs DiffEngineTray at system startup.
By default, when a diff is opened, the temp file will be on the left and the target file will be on the right. To invert this, select "Open on left".
+#### Max instances to launch
+
+Control the [max instances to launch setting](docs/diff-tool.md#maxinstancestolaunch).
+
+
#### Accept all HotKey
Registers a system wide HotKey to accept pending:
diff --git a/docs/tray.md b/docs/tray.md
index 5fdcd53b..5f63743f 100644
--- a/docs/tray.md
+++ b/docs/tray.md
@@ -76,6 +76,11 @@ Runs DiffEngineTray at system startup.
By default, when a diff is opened, the temp file will be on the left and the target file will be on the right. To invert this, select "Open on left".
+#### Max instances to launch
+
+Control the [max instances to launch setting](docs/diff-tool.md#maxinstancestolaunch).
+
+
#### Accept all HotKey
Registers a system wide HotKey to accept pending:
diff --git a/src/DiffEngine/DiffRunner.cs b/src/DiffEngine/DiffRunner.cs
index ed4a7f7a..0d2fb36e 100644
--- a/src/DiffEngine/DiffRunner.cs
+++ b/src/DiffEngine/DiffRunner.cs
@@ -16,8 +16,7 @@ public static partial class DiffRunner
public static void MaxInstancesToLaunch(int value)
{
- Guard.AgainstNegativeAndZero(value, nameof(value));
- MaxInstance.Set(value);
+ MaxInstance.SetForAppDomain(value);
}
public static LaunchResult Launch(DiffTool tool, string tempFile, string targetFile)
diff --git a/src/DiffEngine/Guard.cs b/src/DiffEngine/Guard.cs
index 75845d4c..0784b3dd 100644
--- a/src/DiffEngine/Guard.cs
+++ b/src/DiffEngine/Guard.cs
@@ -29,7 +29,7 @@ public static void AgainstEmpty(string value, string argumentName)
}
}
- public static void AgainstEmpty(object[] value, string argumentName)
+ public static void AgainstEmpty(object?[] value, string argumentName)
{
if (value == null)
{
diff --git a/src/DiffEngine/MaxInstance.cs b/src/DiffEngine/MaxInstance.cs
index cb2ca954..bc9cdfd4 100644
--- a/src/DiffEngine/MaxInstance.cs
+++ b/src/DiffEngine/MaxInstance.cs
@@ -3,15 +3,16 @@
static class MaxInstance
{
- static int maxInstancesToLaunch = GetMaxInstances();
+ public static int MaxInstancesToLaunch { get; private set; } = GetMaxInstances();
static int launchedInstances;
+ const int defaultMax = 5;
static int GetMaxInstances()
{
var variable = Environment.GetEnvironmentVariable("DiffEngine_MaxInstances");
if (string.IsNullOrEmpty(variable))
{
- return 5;
+ return defaultMax;
}
if (ushort.TryParse(variable, out var result))
@@ -22,15 +23,35 @@ static int GetMaxInstances()
throw new($"Could not parse the DiffEngine_MaxInstances environment variable: {variable}");
}
- public static void Set(int value)
+ public static void SetForAppDomain(int value)
{
Guard.AgainstNegativeAndZero(value, nameof(value));
- maxInstancesToLaunch = value;
+ MaxInstancesToLaunch = value;
+ }
+
+ public static void SetForUser(int value)
+ {
+ if (MaxInstancesToLaunch == value)
+ {
+ return;
+ }
+ MaxInstancesToLaunch = value;
+ string? envVariable;
+ if (value == defaultMax)
+ {
+ envVariable = null;
+ }
+ else
+ {
+ envVariable = value.ToString();
+ }
+
+ Environment.SetEnvironmentVariable("DiffEngine_MaxInstances", envVariable, EnvironmentVariableTarget.User);
}
public static bool Reached()
{
var instanceCount = Interlocked.Increment(ref launchedInstances);
- return instanceCount > maxInstancesToLaunch;
+ return instanceCount > MaxInstancesToLaunch;
}
}
\ No newline at end of file
diff --git a/src/DiffEngine/ResolvedTool.cs b/src/DiffEngine/ResolvedTool.cs
index f49b8616..ce9bc4e9 100644
--- a/src/DiffEngine/ResolvedTool.cs
+++ b/src/DiffEngine/ResolvedTool.cs
@@ -30,7 +30,7 @@ public string BuildCommand(string tempFile, string targetFile)
string GetArguments(string tempFile, string targetFile)
{
- if (TargetPositionHelper.TargetOnLeft)
+ if (TargetPosition.TargetOnLeft)
{
return TargetLeftArguments(tempFile, targetFile);
}
diff --git a/src/DiffEngine/TargetPositionHelper.cs b/src/DiffEngine/TargetPosition.cs
similarity index 88%
rename from src/DiffEngine/TargetPositionHelper.cs
rename to src/DiffEngine/TargetPosition.cs
index 6ca02f7d..e7241dc1 100644
--- a/src/DiffEngine/TargetPositionHelper.cs
+++ b/src/DiffEngine/TargetPosition.cs
@@ -1,10 +1,10 @@
using System;
-static class TargetPositionHelper
+static class TargetPosition
{
public static bool TargetOnLeft { get; private set; }
- static TargetPositionHelper()
+ static TargetPosition()
{
TargetOnLeft = ReadTargetOnLeft().GetValueOrDefault(false);
}
@@ -33,6 +33,11 @@ static TargetPositionHelper()
public static void SetTargetOnLeft(bool value)
{
+ if (TargetOnLeft == value)
+ {
+ return;
+ }
+
TargetOnLeft = value;
string? envVariable;
if (value)
diff --git a/src/DiffEngineTray.Tests/OptionsFormTests.Default.verified.png b/src/DiffEngineTray.Tests/OptionsFormTests.Default.verified.png
index 39331afb..9051f6fe 100644
Binary files a/src/DiffEngineTray.Tests/OptionsFormTests.Default.verified.png and b/src/DiffEngineTray.Tests/OptionsFormTests.Default.verified.png differ
diff --git a/src/DiffEngineTray.Tests/OptionsFormTests.WithKeys.verified.png b/src/DiffEngineTray.Tests/OptionsFormTests.WithKeys.verified.png
index 971c787a..f96ddd39 100644
Binary files a/src/DiffEngineTray.Tests/OptionsFormTests.WithKeys.verified.png and b/src/DiffEngineTray.Tests/OptionsFormTests.WithKeys.verified.png differ
diff --git a/src/DiffEngineTray.Tests/SettingsHelperTests.ReadWrite.verified.txt b/src/DiffEngineTray.Tests/SettingsHelperTests.ReadWrite.verified.txt
index 90191a1f..390dfe51 100644
--- a/src/DiffEngineTray.Tests/SettingsHelperTests.ReadWrite.verified.txt
+++ b/src/DiffEngineTray.Tests/SettingsHelperTests.ReadWrite.verified.txt
@@ -1,5 +1,6 @@
-{
+{
AcceptAllHotKey: {
Key: T
- }
+ },
+ MaxInstancesToLaunch: 5
}
\ No newline at end of file
diff --git a/src/DiffEngineTray/DiffEngineTray.csproj b/src/DiffEngineTray/DiffEngineTray.csproj
index 36382d1b..207a8a01 100644
--- a/src/DiffEngineTray/DiffEngineTray.csproj
+++ b/src/DiffEngineTray/DiffEngineTray.csproj
@@ -28,7 +28,9 @@
-
+
+
+
diff --git a/src/DiffEngineTray/Settings/OptionsForm.Designer.cs b/src/DiffEngineTray/Settings/OptionsForm.Designer.cs
index 3417aa5f..e3d83701 100644
--- a/src/DiffEngineTray/Settings/OptionsForm.Designer.cs
+++ b/src/DiffEngineTray/Settings/OptionsForm.Designer.cs
@@ -26,9 +26,14 @@ void InitializeComponent()
this.flowLayoutPanel1 = new System.Windows.Forms.FlowLayoutPanel();
this.updateButton = new System.Windows.Forms.Button();
this.targetOnLeftCheckBox = new System.Windows.Forms.CheckBox();
+ this.maxInstancesGroupBox = new System.Windows.Forms.GroupBox();
+ this.maxInstancesNumericUpDown = new System.Windows.Forms.NumericUpDown();
+ this.label1 = new System.Windows.Forms.Label();
this.bottomPanel.SuspendLayout();
this.groupBox1.SuspendLayout();
this.flowLayoutPanel1.SuspendLayout();
+ this.maxInstancesGroupBox.SuspendLayout();
+ ((System.ComponentModel.ISupportInitialize)(this.maxInstancesNumericUpDown)).BeginInit();
this.SuspendLayout();
//
// bottomPanel
@@ -38,17 +43,17 @@ void InitializeComponent()
this.bottomPanel.Controls.Add(this.save);
this.bottomPanel.Dock = System.Windows.Forms.DockStyle.Bottom;
this.bottomPanel.FlowDirection = System.Windows.Forms.FlowDirection.RightToLeft;
- this.bottomPanel.Location = new System.Drawing.Point(5, 451);
+ this.bottomPanel.Location = new System.Drawing.Point(5, 508);
this.bottomPanel.Margin = new System.Windows.Forms.Padding(2);
this.bottomPanel.Name = "bottomPanel";
- this.bottomPanel.Size = new System.Drawing.Size(471, 29);
+ this.bottomPanel.Size = new System.Drawing.Size(507, 29);
this.bottomPanel.TabIndex = 1;
//
// cancel
//
this.cancel.AutoSize = true;
this.cancel.DialogResult = System.Windows.Forms.DialogResult.Cancel;
- this.cancel.Location = new System.Drawing.Point(389, 2);
+ this.cancel.Location = new System.Drawing.Point(425, 2);
this.cancel.Margin = new System.Windows.Forms.Padding(2);
this.cancel.Name = "cancel";
this.cancel.RightToLeft = System.Windows.Forms.RightToLeft.Yes;
@@ -60,7 +65,7 @@ void InitializeComponent()
// save
//
this.save.AutoSize = true;
- this.save.Location = new System.Drawing.Point(305, 2);
+ this.save.Location = new System.Drawing.Point(341, 2);
this.save.Margin = new System.Windows.Forms.Padding(2);
this.save.Name = "save";
this.save.Size = new System.Drawing.Size(80, 25);
@@ -76,11 +81,11 @@ void InitializeComponent()
this.acceptAllHotKey.Help = "Accept pending deletes and pending moves";
this.acceptAllHotKey.HotKey = null;
this.acceptAllHotKey.Label = "Accept all HotKey";
- this.acceptAllHotKey.Location = new System.Drawing.Point(5, 58);
+ this.acceptAllHotKey.Location = new System.Drawing.Point(5, 140);
this.acceptAllHotKey.Margin = new System.Windows.Forms.Padding(2);
this.acceptAllHotKey.Name = "acceptAllHotKey";
this.acceptAllHotKey.Padding = new System.Windows.Forms.Padding(3);
- this.acceptAllHotKey.Size = new System.Drawing.Size(471, 114);
+ this.acceptAllHotKey.Size = new System.Drawing.Size(507, 114);
this.acceptAllHotKey.TabIndex = 2;
this.acceptAllHotKey.TabStop = false;
//
@@ -92,7 +97,7 @@ void InitializeComponent()
this.startupCheckBox.Margin = new System.Windows.Forms.Padding(2);
this.startupCheckBox.Name = "startupCheckBox";
this.startupCheckBox.Padding = new System.Windows.Forms.Padding(5, 4, 5, 4);
- this.startupCheckBox.Size = new System.Drawing.Size(471, 27);
+ this.startupCheckBox.Size = new System.Drawing.Size(507, 27);
this.startupCheckBox.TabIndex = 3;
this.startupCheckBox.Text = "Run at startup";
this.startupCheckBox.UseVisualStyleBackColor = true;
@@ -104,10 +109,10 @@ void InitializeComponent()
this.groupBox1.Controls.Add(this.trayDocsLink);
this.groupBox1.Controls.Add(this.diffEngineLink);
this.groupBox1.Dock = System.Windows.Forms.DockStyle.Top;
- this.groupBox1.Location = new System.Drawing.Point(5, 316);
+ this.groupBox1.Location = new System.Drawing.Point(5, 398);
this.groupBox1.Name = "groupBox1";
this.groupBox1.Padding = new System.Windows.Forms.Padding(6, 5, 6, 5);
- this.groupBox1.Size = new System.Drawing.Size(471, 89);
+ this.groupBox1.Size = new System.Drawing.Size(507, 89);
this.groupBox1.TabIndex = 5;
this.groupBox1.TabStop = false;
this.groupBox1.Text = "More information:";
@@ -158,11 +163,11 @@ void InitializeComponent()
" Rider, or Visual Studio Code.";
this.acceptOpenHotKey.HotKey = null;
this.acceptOpenHotKey.Label = "Accept all open HotKey";
- this.acceptOpenHotKey.Location = new System.Drawing.Point(5, 172);
+ this.acceptOpenHotKey.Location = new System.Drawing.Point(5, 254);
this.acceptOpenHotKey.Margin = new System.Windows.Forms.Padding(2);
this.acceptOpenHotKey.Name = "acceptOpenHotKey";
this.acceptOpenHotKey.Padding = new System.Windows.Forms.Padding(3);
- this.acceptOpenHotKey.Size = new System.Drawing.Size(471, 144);
+ this.acceptOpenHotKey.Size = new System.Drawing.Size(507, 144);
this.acceptOpenHotKey.TabIndex = 6;
this.acceptOpenHotKey.TabStop = false;
//
@@ -171,11 +176,11 @@ void InitializeComponent()
this.flowLayoutPanel1.AutoSize = true;
this.flowLayoutPanel1.Controls.Add(this.updateButton);
this.flowLayoutPanel1.Dock = System.Windows.Forms.DockStyle.Top;
- this.flowLayoutPanel1.Location = new System.Drawing.Point(5, 405);
+ this.flowLayoutPanel1.Location = new System.Drawing.Point(5, 487);
this.flowLayoutPanel1.Margin = new System.Windows.Forms.Padding(2);
this.flowLayoutPanel1.Name = "flowLayoutPanel1";
this.flowLayoutPanel1.Padding = new System.Windows.Forms.Padding(3, 2, 3, 2);
- this.flowLayoutPanel1.Size = new System.Drawing.Size(471, 33);
+ this.flowLayoutPanel1.Size = new System.Drawing.Size(507, 33);
this.flowLayoutPanel1.TabIndex = 7;
//
// updateButton
@@ -198,10 +203,54 @@ void InitializeComponent()
this.targetOnLeftCheckBox.Margin = new System.Windows.Forms.Padding(2);
this.targetOnLeftCheckBox.Name = "targetOnLeftCheckBox";
this.targetOnLeftCheckBox.Padding = new System.Windows.Forms.Padding(5, 4, 5, 4);
- this.targetOnLeftCheckBox.Size = new System.Drawing.Size(471, 27);
+ this.targetOnLeftCheckBox.Size = new System.Drawing.Size(507, 27);
this.targetOnLeftCheckBox.TabIndex = 8;
this.targetOnLeftCheckBox.Text = "Open target on left. The default is temp on left and target on right";
this.targetOnLeftCheckBox.UseVisualStyleBackColor = true;
+ //
+ // maxInstancesGroupBox
+ //
+ this.maxInstancesGroupBox.Controls.Add(this.maxInstancesNumericUpDown);
+ this.maxInstancesGroupBox.Controls.Add(this.label1);
+ this.maxInstancesGroupBox.Dock = System.Windows.Forms.DockStyle.Top;
+ this.maxInstancesGroupBox.Location = new System.Drawing.Point(5, 58);
+ this.maxInstancesGroupBox.Name = "maxInstancesGroupBox";
+ this.maxInstancesGroupBox.Padding = new System.Windows.Forms.Padding(5);
+ this.maxInstancesGroupBox.Size = new System.Drawing.Size(507, 82);
+ this.maxInstancesGroupBox.TabIndex = 9;
+ this.maxInstancesGroupBox.TabStop = false;
+ this.maxInstancesGroupBox.Text = "Max instances to launch";
+ //
+ // maxInstancesNumericUpDown
+ //
+ this.maxInstancesNumericUpDown.Dock = System.Windows.Forms.DockStyle.Left;
+ this.maxInstancesNumericUpDown.Location = new System.Drawing.Point(5, 44);
+ this.maxInstancesNumericUpDown.Margin = new System.Windows.Forms.Padding(5);
+ this.maxInstancesNumericUpDown.Minimum = new decimal(new int[] {
+ 1,
+ 0,
+ 0,
+ 0});
+ this.maxInstancesNumericUpDown.Name = "maxInstancesNumericUpDown";
+ this.maxInstancesNumericUpDown.Size = new System.Drawing.Size(62, 23);
+ this.maxInstancesNumericUpDown.TabIndex = 0;
+ this.maxInstancesNumericUpDown.Value = new decimal(new int[] {
+ 1,
+ 0,
+ 0,
+ 0});
+ //
+ // label1
+ //
+ this.label1.AutoSize = true;
+ this.label1.Dock = System.Windows.Forms.DockStyle.Top;
+ this.label1.Location = new System.Drawing.Point(5, 21);
+ this.label1.Name = "label1";
+ this.label1.Padding = new System.Windows.Forms.Padding(3, 3, 3, 5);
+ this.label1.Size = new System.Drawing.Size(473, 23);
+ this.label1.TabIndex = 1;
+ this.label1.Text = "To minimize the impact on system resources, the maximum diffs to launch is restri" +
+ "cted.";
//
// OptionsForm
//
@@ -210,12 +259,13 @@ void InitializeComponent()
this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
this.AutoSize = true;
this.CancelButton = this.cancel;
- this.ClientSize = new System.Drawing.Size(481, 484);
+ this.ClientSize = new System.Drawing.Size(517, 541);
this.Controls.Add(this.flowLayoutPanel1);
this.Controls.Add(this.groupBox1);
this.Controls.Add(this.bottomPanel);
this.Controls.Add(this.acceptOpenHotKey);
this.Controls.Add(this.acceptAllHotKey);
+ this.Controls.Add(this.maxInstancesGroupBox);
this.Controls.Add(this.targetOnLeftCheckBox);
this.Controls.Add(this.startupCheckBox);
this.FormBorderStyle = System.Windows.Forms.FormBorderStyle.FixedDialog;
@@ -233,6 +283,9 @@ void InitializeComponent()
this.groupBox1.PerformLayout();
this.flowLayoutPanel1.ResumeLayout(false);
this.flowLayoutPanel1.PerformLayout();
+ this.maxInstancesGroupBox.ResumeLayout(false);
+ this.maxInstancesGroupBox.PerformLayout();
+ ((System.ComponentModel.ISupportInitialize)(this.maxInstancesNumericUpDown)).EndInit();
this.ResumeLayout(false);
this.PerformLayout();
@@ -250,4 +303,7 @@ void InitializeComponent()
private System.Windows.Forms.FlowLayoutPanel flowLayoutPanel1;
private System.Windows.Forms.Button updateButton;
private System.Windows.Forms.CheckBox targetOnLeftCheckBox;
+ private System.Windows.Forms.GroupBox maxInstancesGroupBox;
+ private System.Windows.Forms.NumericUpDown maxInstancesNumericUpDown;
+ private System.Windows.Forms.Label label1;
}
\ No newline at end of file
diff --git a/src/DiffEngineTray/Settings/OptionsForm.cs b/src/DiffEngineTray/Settings/OptionsForm.cs
index 7fa8da72..ed066196 100644
--- a/src/DiffEngineTray/Settings/OptionsForm.cs
+++ b/src/DiffEngineTray/Settings/OptionsForm.cs
@@ -25,6 +25,7 @@ public OptionsForm(Settings settings, Func>
acceptOpenHotKey.HotKey = settings.AcceptOpenHotKey;
startupCheckBox.Checked = settings.RunAtStartup;
targetOnLeftCheckBox.Checked = settings.TargetOnLeft;
+ maxInstancesNumericUpDown.Value = settings.MaxInstancesToLaunch;
}
async void save_Click(object sender, EventArgs e)
@@ -34,7 +35,8 @@ async void save_Click(object sender, EventArgs e)
TargetOnLeft = targetOnLeftCheckBox.Checked,
RunAtStartup = startupCheckBox.Checked,
AcceptAllHotKey = acceptAllHotKey.HotKey,
- AcceptOpenHotKey = acceptOpenHotKey.HotKey
+ AcceptOpenHotKey = acceptOpenHotKey.HotKey,
+ MaxInstancesToLaunch = (int)maxInstancesNumericUpDown.Value
};
var errors = (await trySave(newSettings)).ToList();
diff --git a/src/DiffEngineTray/Settings/Settings.cs b/src/DiffEngineTray/Settings/Settings.cs
index 16db46fc..f9ff1e11 100644
--- a/src/DiffEngineTray/Settings/Settings.cs
+++ b/src/DiffEngineTray/Settings/Settings.cs
@@ -4,4 +4,5 @@ public class Settings
public HotKey? AcceptOpenHotKey { get; set; }
public bool RunAtStartup { get; set; }
public bool TargetOnLeft { get; set; }
+ public int MaxInstancesToLaunch { get; set; } = MaxInstance.MaxInstancesToLaunch;
}
\ No newline at end of file
diff --git a/src/DiffEngineTray/Settings/SettingsHelper.cs b/src/DiffEngineTray/Settings/SettingsHelper.cs
index e7d506c5..d28fa46c 100644
--- a/src/DiffEngineTray/Settings/SettingsHelper.cs
+++ b/src/DiffEngineTray/Settings/SettingsHelper.cs
@@ -29,13 +29,15 @@ public static async Task Read()
settings = new();
}
- settings.TargetOnLeft = TargetPositionHelper.TargetOnLeft;
+ settings.TargetOnLeft = TargetPosition.TargetOnLeft;
+ settings.MaxInstancesToLaunch = MaxInstance.MaxInstancesToLaunch;
return settings;
}
public static async Task Write(Settings settings)
{
- TargetPositionHelper.SetTargetOnLeft(settings.TargetOnLeft);
+ TargetPosition.SetTargetOnLeft(settings.TargetOnLeft);
+ MaxInstance.SetForUser(settings.MaxInstancesToLaunch);
File.Delete(FilePath);
await using var stream = File.OpenWrite(FilePath);
await JsonSerializer.SerializeAsync(stream, settings);
diff --git a/src/Directory.Build.props b/src/Directory.Build.props
index 66a112ef..65dad285 100644
--- a/src/Directory.Build.props
+++ b/src/Directory.Build.props
@@ -2,7 +2,7 @@
CS1591;CS0649
- 7.0.0
+ 7.1.0
1.0.0
Testing, Snapshot, Diff, Compare
Launches diff tools based on file extensions. Designed to be consumed by snapshot testing libraries.