diff --git a/extensions/git/src/repository.ts b/extensions/git/src/repository.ts
index e96d54d708e6167f444a5d47762784ed1e97a131..abdd8184ffaa6efc3cd4548361b1f35ae0397d46 100644
--- a/extensions/git/src/repository.ts
+++ b/extensions/git/src/repository.ts
@@ -519,6 +519,7 @@ export class Repository implements Disposable {
 		this._sourceControl.inputBox.placeholder = localize('commitMessage', "Message (press {0} to commit)");
 		this._sourceControl.acceptInputCommand = { command: 'git.commitWithInput', title: localize('commit', "Commit"), arguments: [this._sourceControl] };
 		this._sourceControl.quickDiffProvider = this;
+		this._sourceControl.inputBox.warningLength = 72;
 		this.disposables.push(this._sourceControl);
 
 		this._mergeGroup = this._sourceControl.createResourceGroup('merge', localize('merge changes', "Merge Changes"));
diff --git a/src/vs/vscode.d.ts b/src/vs/vscode.d.ts
index b02773f70b9966ef2bc00d90bbdd5812515bffef..3198839661814b78da6997e35f547a4b5f1ef5db 100644
--- a/src/vs/vscode.d.ts
+++ b/src/vs/vscode.d.ts
@@ -5782,6 +5782,11 @@ declare module 'vscode' {
 		 * A string to show as place holder in the input box to guide the user.
 		 */
 		placeholder: string;
+
+		/**
+		 * The warning threshold for commit messages.
+		 */
+		warningLength: number | undefined;
 	}
 
 	interface QuickDiffProvider {
diff --git a/src/vs/workbench/api/electron-browser/mainThreadSCM.ts b/src/vs/workbench/api/electron-browser/mainThreadSCM.ts
index 88c6377b3c46a08057eeb6eb0668a358bc3b11a5..7e728e798bddf7df3b5e0a974c3731ede619db42 100644
--- a/src/vs/workbench/api/electron-browser/mainThreadSCM.ts
+++ b/src/vs/workbench/api/electron-browser/mainThreadSCM.ts
@@ -391,4 +391,14 @@ export class MainThreadSCM implements MainThreadSCMShape {
 
 		repository.input.placeholder = placeholder;
 	}
+
+	$setWarningLength(sourceControlHandle: number, warningLength: number): void {
+		const repository = this._repositories[sourceControlHandle];
+
+		if (!repository) {
+			return;
+		}
+
+		repository.input.warningLength = warningLength;
+	}
 }
diff --git a/src/vs/workbench/api/node/extHost.protocol.ts b/src/vs/workbench/api/node/extHost.protocol.ts
index 111a4643be84edf11d8bdc0e8b830fdb139c9274..d3efe056b8dbd6aa440e961dedfbf8fb4189ccab 100644
--- a/src/vs/workbench/api/node/extHost.protocol.ts
+++ b/src/vs/workbench/api/node/extHost.protocol.ts
@@ -410,6 +410,7 @@ export interface MainThreadSCMShape extends IDisposable {
 
 	$setInputBoxValue(sourceControlHandle: number, value: string): void;
 	$setInputBoxPlaceholder(sourceControlHandle: number, placeholder: string): void;
+	$setWarningLength(sourceControlHandle: number, warningLength: number): void;
 }
 
 export type DebugSessionUUID = string;
diff --git a/src/vs/workbench/api/node/extHostSCM.ts b/src/vs/workbench/api/node/extHostSCM.ts
index 9444ef007441510abd29a0ee148111b62bd50c80..2f8ea94d5b69fceb9ddc75290f6c85b6669336d4 100644
--- a/src/vs/workbench/api/node/extHostSCM.ts
+++ b/src/vs/workbench/api/node/extHostSCM.ts
@@ -110,7 +110,7 @@ function compareResourceStates(a: vscode.SourceControlResourceState, b: vscode.S
 	return result;
 }
 
-export class ExtHostSCMInputBox {
+export class ExtHostSCMInputBox implements vscode.SourceControlInputBox {
 
 	private _value: string = '';
 
@@ -140,6 +140,17 @@ export class ExtHostSCMInputBox {
 		this._placeholder = placeholder;
 	}
 
+	private _warningLength: number | undefined;
+
+	get warningLength(): number | undefined {
+		return this._warningLength;
+	}
+
+	set warningLength(warningLength: number) {
+		this._proxy.$setWarningLength(this._sourceControlHandle, warningLength);
+		this._warningLength = warningLength;
+	}
+
 	constructor(private _proxy: MainThreadSCMShape, private _sourceControlHandle: number) {
 		// noop
 	}
diff --git a/src/vs/workbench/parts/scm/electron-browser/scmViewlet.ts b/src/vs/workbench/parts/scm/electron-browser/scmViewlet.ts
index 4530cff6727f2dd7ebe0b3d77ce5af8e851fda9e..982d059e3375987e8bdea894699f2846f13b30d5 100644
--- a/src/vs/workbench/parts/scm/electron-browser/scmViewlet.ts
+++ b/src/vs/workbench/parts/scm/electron-browser/scmViewlet.ts
@@ -45,7 +45,7 @@ import { IWorkspaceContextService } from 'vs/platform/workspace/common/workspace
 import { IStorageService } from 'vs/platform/storage/common/storage';
 import { IViewletService } from 'vs/workbench/services/viewlet/browser/viewlet';
 import { IExtensionsViewlet, VIEWLET_ID as EXTENSIONS_VIEWLET_ID } from 'vs/workbench/parts/extensions/common/extensions';
-import { InputBox } from 'vs/base/browser/ui/inputbox/inputBox';
+import { IMessage, InputBox, MessageType } from 'vs/base/browser/ui/inputbox/inputBox';
 import { StandardKeyboardEvent } from 'vs/base/browser/keyboardEvent';
 import { KeyMod, KeyCode } from 'vs/base/common/keyCodes';
 import { Command } from 'vs/editor/common/modes';
@@ -753,7 +753,33 @@ export class RepositoryPanel extends ViewletPanel {
 			this.inputBox.setPlaceHolder(placeholder);
 		};
 
-		this.inputBox = new InputBox(this.inputBoxContainer, this.contextViewService, { flexibleHeight: true });
+		const validation = (text: string): IMessage => {
+			const warningLength = this.repository.input.warningLength;
+			if (warningLength === undefined) {
+				return {
+					content: localize('commitMessageInfo', "{0} characters", text.length),
+					type: MessageType.INFO
+				};
+			}
+
+			const charactersLeft = warningLength - text.length;
+			if (charactersLeft > 0) {
+				return {
+					content: localize('commitMessageCountdown', "{0} characters left", text.length),
+					type: MessageType.INFO
+				};
+			} else {
+				return {
+					content: localize('commitMessageWarning', "{0} characters over", text.length),
+					type: MessageType.WARNING
+				};
+			}
+		};
+
+		this.inputBox = new InputBox(this.inputBoxContainer, this.contextViewService, {
+			flexibleHeight: true,
+			validationOptions: { validation: validation }
+		});
 		this.disposables.push(attachInputBoxStyler(this.inputBox, this.themeService));
 		this.disposables.push(this.inputBox);
 
diff --git a/src/vs/workbench/services/scm/common/scm.ts b/src/vs/workbench/services/scm/common/scm.ts
index 78c1252f599ec96ccb1e9c3fc4624cf085476a09..b10ab4dc7cc54c3c0aef2526d49a49b5a3de4c55 100644
--- a/src/vs/workbench/services/scm/common/scm.ts
+++ b/src/vs/workbench/services/scm/common/scm.ts
@@ -74,6 +74,8 @@ export interface ISCMInput {
 
 	placeholder: string;
 	readonly onDidChangePlaceholder: Event<string>;
+
+	warningLength: number | undefined;
 }
 
 export interface ISCMRepository extends IDisposable {
diff --git a/src/vs/workbench/services/scm/common/scmService.ts b/src/vs/workbench/services/scm/common/scmService.ts
index db569fc7c5774046870874822deb2987c99d564e..a16e88a7436623b91f69d77396e46226e1cdf11e 100644
--- a/src/vs/workbench/services/scm/common/scmService.ts
+++ b/src/vs/workbench/services/scm/common/scmService.ts
@@ -39,6 +39,16 @@ class SCMInput implements ISCMInput {
 
 	private _onDidChangePlaceholder = new Emitter<string>();
 	get onDidChangePlaceholder(): Event<string> { return this._onDidChangePlaceholder.event; }
+
+	private _warningLength: number | undefined;
+
+	get warningLength(): number | undefined {
+		return this._warningLength;
+	}
+
+	set warningLength(warningLength: number) {
+		this._warningLength = warningLength;
+	}
 }
 
 class SCMRepository implements ISCMRepository {
@@ -106,4 +116,4 @@ export class SCMService implements ISCMService {
 
 		return repository;
 	}
-}
\ No newline at end of file
+}