Add apply-patch, basic revert and cherry-pick functionality (#17902)

This code adds a simple endpoint to apply patches to repositories and
branches on gitea. This is then used along with the conflicting checking
code in #18004 to provide a basic implementation of cherry-pick revert.

Now because the buttons necessary for cherry-pick and revert have 
required us to create a dropdown next to the Browse Source button
I've also implemented Create Branch and Create Tag operations.

Fix #3880 
Fix #17986 

Signed-off-by: Andrew Thornton <art27@cantab.net>

2 files changed, 108 insertions, 0 deletions

diff --git a/routers/api/v1/api.go b/routers/api/v1/api.go
index df00a852f2..6d8ab8ce98 100644
--- a/routers/api/v1/api.go
+++ b/routers/api/v1/api.go
@@ -975,6 +975,7 @@ func Routes(sessioner func(http.Handler) http.Handler) *web.Route {
 					m.Get("/tags/{sha}", context.RepoRefForAPI, repo.GetAnnotatedTag)
 					m.Get("/notes/{sha}", repo.GetNote)
 				}, reqRepoReader(unit.TypeCode))
+				m.Post("/diffpatch", reqRepoWriter(unit.TypeCode), reqToken(), bind(api.ApplyDiffPatchFileOptions{}), repo.ApplyDiffPatch)
 				m.Group("/contents", func() {
 					m.Get("", repo.GetContentsList)
 					m.Get("/*", repo.GetContents)
diff --git a/routers/api/v1/repo/patch.go b/routers/api/v1/repo/patch.go
new file mode 100644
index 0000000000..64a7a32d16
--- /dev/null
+++ b/routers/api/v1/repo/patch.go
@@ -0,0 +1,107 @@
+// Copyright 2021 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package repo
+
+import (
+	"net/http"
+	"time"
+
+	"code.gitea.io/gitea/models"
+	"code.gitea.io/gitea/modules/context"
+	"code.gitea.io/gitea/modules/git"
+	api "code.gitea.io/gitea/modules/structs"
+	"code.gitea.io/gitea/modules/web"
+	"code.gitea.io/gitea/services/repository/files"
+)
+
+// ApplyDiffPatch handles API call for applying a patch
+func ApplyDiffPatch(ctx *context.APIContext) {
+	// swagger:operation POST /repos/{owner}/{repo}/diffpatch repository repoApplyDiffPatch
+	// ---
+	// summary: Apply diff patch to repository
+	// consumes:
+	// - application/json
+	// produces:
+	// - application/json
+	// parameters:
+	// - name: owner
+	//   in: path
+	//   description: owner of the repo
+	//   type: string
+	//   required: true
+	// - name: repo
+	//   in: path
+	//   description: name of the repo
+	//   type: string
+	//   required: true
+	// - name: body
+	//   in: body
+	//   required: true
+	//   schema:
+	//     "$ref": "#/definitions/UpdateFileOptions"
+	// responses:
+	//   "200":
+	//     "$ref": "#/responses/FileResponse"
+	apiOpts := web.GetForm(ctx).(*api.ApplyDiffPatchFileOptions)
+
+	opts := &files.ApplyDiffPatchOptions{
+		Content:   apiOpts.Content,
+		SHA:       apiOpts.SHA,
+		Message:   apiOpts.Message,
+		OldBranch: apiOpts.BranchName,
+		NewBranch: apiOpts.NewBranchName,
+		Committer: &files.IdentityOptions{
+			Name:  apiOpts.Committer.Name,
+			Email: apiOpts.Committer.Email,
+		},
+		Author: &files.IdentityOptions{
+			Name:  apiOpts.Author.Name,
+			Email: apiOpts.Author.Email,
+		},
+		Dates: &files.CommitDateOptions{
+			Author:    apiOpts.Dates.Author,
+			Committer: apiOpts.Dates.Committer,
+		},
+		Signoff: apiOpts.Signoff,
+	}
+	if opts.Dates.Author.IsZero() {
+		opts.Dates.Author = time.Now()
+	}
+	if opts.Dates.Committer.IsZero() {
+		opts.Dates.Committer = time.Now()
+	}
+
+	if opts.Message == "" {
+		opts.Message = "apply-patch"
+	}
+
+	if !canWriteFiles(ctx.Repo) {
+		ctx.Error(http.StatusInternalServerError, "ApplyPatch", models.ErrUserDoesNotHaveAccessToRepo{
+			UserID:   ctx.User.ID,
+			RepoName: ctx.Repo.Repository.LowerName,
+		})
+		return
+	}
+
+	fileResponse, err := files.ApplyDiffPatch(ctx, ctx.Repo.Repository, ctx.User, opts)
+	if err != nil {
+		if models.IsErrUserCannotCommit(err) || models.IsErrFilePathProtected(err) {
+			ctx.Error(http.StatusForbidden, "Access", err)
+			return
+		}
+		if models.IsErrBranchAlreadyExists(err) || models.IsErrFilenameInvalid(err) || models.IsErrSHADoesNotMatch(err) ||
+			models.IsErrFilePathInvalid(err) || models.IsErrRepoFileAlreadyExists(err) {
+			ctx.Error(http.StatusUnprocessableEntity, "Invalid", err)
+			return
+		}
+		if models.IsErrBranchDoesNotExist(err) || git.IsErrBranchNotExist(err) {
+			ctx.Error(http.StatusNotFound, "BranchDoesNotExist", err)
+			return
+		}
+		ctx.Error(http.StatusInternalServerError, "ApplyPatch", err)
+	} else {
+		ctx.JSON(http.StatusCreated, fileResponse)
+	}
+}