Support amending of initial commit

Signed-off-by: Nigel Westbury <nigelipse@miegel.org>

packages/git/src/browser/git-scm-provider.ts

@@ -394,9 +394,11 @@ export namespace GitScmProvider {
 
 export class GitAmendSupport implements ScmAmendSupport {
 
-    constructor(protected readonly repository: Repository, protected readonly git: Git) { }
+    constructor(
+        protected readonly repository: Repository,
+        protected readonly git: Git) { }
 
-    public async getInitialAmendingCommits(amendingHeadCommitSha: string, latestCommitSha: string): Promise<ScmCommit[]> {
+    public async getInitialAmendingCommits(amendingHeadCommitSha: string, latestCommitSha: string | undefined): Promise<ScmCommit[]> {
         const commits = await this.git.log(
             this.repository,
             {
@@ -414,7 +416,16 @@ export class GitAmendSupport implements ScmAmendSupport {
     }
 
     public async reset(commit: string): Promise<void> {
-        await this.git.exec(this.repository, ['reset', commit, '--soft']);
+        if (commit === 'HEAD~' && await this.isHeadInitialCommit()) {
+            await this.git.exec(this.repository, ['update-ref', '-d', 'HEAD']);
+        } else {
+            await this.git.exec(this.repository, ['reset', commit, '--soft']);
+        }
+    }
+
+    protected async isHeadInitialCommit(): Promise<boolean> {
+        const result = await this.git.revParse(this.repository, { ref: 'HEAD~' });
+        return !result;
     }
 
     public async getLastCommit(): Promise<ScmCommit | undefined> {

packages/scm/src/browser/scm-amend-component.tsx

@@ -98,6 +98,8 @@ export class ScmAmendComponent extends React.Component<ScmAmendComponentProps, S
     }
 
     async fetchStatusAndSetState(): Promise<void> {
+        const storageKey = this.getStorageKey();
+
         const nextCommit = await this.getLastCommit();
         if (nextCommit && this.state.lastCommit && nextCommit.commit.id === this.state.lastCommit.commit.id) {
             // No change here
@@ -119,32 +121,37 @@ export class ScmAmendComponent extends React.Component<ScmAmendComponentProps, S
             // the view just updates without transition.
             this.setState({ amendingCommits: [], lastCommit: nextCommit });
         } else {
+            const amendingCommits = this.state.amendingCommits.concat([]); // copy the array
+
+            const direction: 'up' | 'down' = this.transitionHint === 'amend' ? 'up' : 'down';
+            switch (this.transitionHint) {
+                case 'amend':
+                    if (this.state.lastCommit) {
+                        amendingCommits.push(this.state.lastCommit);
+
+                        const serializedState = JSON.stringify({
+                            amendingHeadCommitSha: amendingCommits[0].commit.id,
+                            latestCommitSha: nextCommit ? nextCommit.commit.id : undefined
+                        });
+                        this.props.storageService.setData<string | undefined>(storageKey, serializedState);
+                    }
+                    break;
+                case 'unamend':
+                    amendingCommits.pop();
+                    if (amendingCommits.length === 0) {
+                        this.props.storageService.setData<string | undefined>(storageKey, undefined);
+                    } else {
+                        const serializedState = JSON.stringify({
+                            amendingHeadCommitSha: amendingCommits[0].commit.id,
+                            latestCommitSha: nextCommit ? nextCommit.commit.id : undefined
+                        });
+                        this.props.storageService.setData<string | undefined>(storageKey, serializedState);
+                    }
+                    break;
+            }
+
             if (this.state.lastCommit && nextCommit) {
-                const direction: 'up' | 'down' = this.transitionHint === 'amend' ? 'up' : 'down';
                 const transitionData = { direction, previousLastCommit: this.state.lastCommit };
-                const amendingCommits = this.state.amendingCommits.concat([]); // copy the array
-                switch (this.transitionHint) {
-                    case 'amend':
-                        if (this.state.lastCommit) {
-                            amendingCommits.push(this.state.lastCommit);
-
-                            const storageKey = this.getStorageKey();
-                            const serializedState = JSON.stringify({
-                                amendingHeadCommitSha: amendingCommits[0].commit.id,
-                                latestCommitSha: nextCommit.commit.id
-                            });
-                            this.props.storageService.setData<string | undefined>(storageKey, serializedState);
-                        }
-                        break;
-                    case 'unamend':
-                        amendingCommits.pop();
-                        if (amendingCommits.length === 0) {
-                            const storageKey = this.getStorageKey();
-                            this.props.storageService.setData<string | undefined>(storageKey, undefined);
-                        }
-                        break;
-                }
-
                 this.setState({ lastCommit: nextCommit, amendingCommits, transition: { ...transitionData, state: 'start' } });
                 this.onNextFrame(() => {
                     this.setState({ transition: { ...transitionData, state: 'transitioning' } });
@@ -157,7 +164,7 @@ export class ScmAmendComponent extends React.Component<ScmAmendComponentProps, S
                     TRANSITION_TIME_MS);
             } else {
                 // No previous last commit so no transition
-                this.setState({ transition: { state: 'none' }, lastCommit: nextCommit });
+                this.setState({ transition: { state: 'none' }, amendingCommits, lastCommit: nextCommit });
             }
         }
 
@@ -176,14 +183,14 @@ export class ScmAmendComponent extends React.Component<ScmAmendComponentProps, S
         // Restore list of commits from saved amending head commit up through parents until the
         // current commit.  (If we don't reach the current commit, the repository has been changed in such
         // a way then unamending commits can no longer be done).
-        if (storedState && lastCommit) {
+        if (storedState) {
             const { amendingHeadCommitSha, latestCommitSha } = JSON.parse(storedState);
-            if (lastCommit.id !== latestCommitSha) {
+            if (!this.commitsAreEqual(lastCommit, latestCommitSha)) {
                 // The head commit in the repository has changed.  It is not the same commit that was the
                 // head commit after the last 'amend'.
                 return [];
             }
-            const commits = await this.props.scmAmendSupport.getInitialAmendingCommits(amendingHeadCommitSha, lastCommit.id);
+            const commits = await this.props.scmAmendSupport.getInitialAmendingCommits(amendingHeadCommitSha, lastCommit ? lastCommit.id : undefined);
 
             const amendingCommitPromises = commits.map(async commit => {
                 const avatar = await this.props.avatarService.getAvatar(commit.authorEmail);
@@ -199,6 +206,17 @@ export class ScmAmendComponent extends React.Component<ScmAmendComponentProps, S
         return REPOSITORY_STORAGE_KEY + ':' + this.props.repository.provider.rootUri;
     }
 
+    /**
+     * Commits are equal if the ids are equal or if both are undefined.
+     * (If a commit is undefined, it represents the initial empty state of a repository,
+     * before the inital commit).
+     */
+    private commitsAreEqual(lastCommit: ScmCommit | undefined, savedLastCommitId: string | undefined): boolean {
+        return lastCommit
+            ? lastCommit.id === savedLastCommitId
+            : savedLastCommitId === undefined;
+    }
+
     /**
      * This function will update the 'model' (lastCommit, amendingCommits) only
      * when the repository sees the last commit change.

packages/scm/src/browser/scm-provider.ts

@@ -78,7 +78,7 @@ export interface ScmCommit {
 }
 
 export interface ScmAmendSupport {
-    getInitialAmendingCommits(amendingHeadCommitSha: string, latestCommitSha: string): Promise<ScmCommit[]>
+    getInitialAmendingCommits(amendingHeadCommitId: string, latestCommitId: string | undefined): Promise<ScmCommit[]>
     getMessage(commit: string): Promise<string>;
     reset(commit: string): Promise<void>;
     getLastCommit(): Promise<ScmCommit | undefined>;