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Signed-off-by: David Pordomingo <[email protected]>
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‎COMPATIBILITY.md

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@@ -21,7 +21,7 @@ is supported by go-git.
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| **branching and merging** |
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| branch | ✔ |
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| checkout | ✔ | Basic usages of checkout are supported. |
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| merge | ✖ |
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| merge | ✔ | Only supports merges where the merge can be resolved as a fast-forward. Does not support `--no-commit` nor `--allow-unrelated-histories` flags |
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| mergetool | ✖ |
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| stash | ✖ |
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| tag | ✔ |

‎_examples/merge/help-long.msg.go

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package main
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const helpLongMsg = `
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NAME:
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%_COMMAND_NAME_% - Join two commits
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SYNOPSIS:
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usage: %_COMMAND_NAME_% <path> <baseCommitRev> <commitRev> [-m <msg>] [--ff-only]
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[--no-ff] [--no-commit] [--allow-unrelated-histories]
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or: %_COMMAND_NAME_% --help
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params:
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<path> Path to the git repository
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<baseCommitRev> Git revision of the commit that will be the base of the merge
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<commitRev> Git revision of the commit that will be merged over the base
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DESCRIPTION:
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%_COMMAND_NAME_% Incorporates changes from the passed <commitRev> over <baseCommitRev> and moves the HEAD of the repo to the merge commit.
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OPTIONS:
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If no options passed, the merge commit will be avoided if it could be considered as a fast-forward, and if needed, it will be used a default merge commit message.
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-m <msg>
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[NOT IMPLEMENTED]
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Set the commit message to be used for the merge commit (in case one is created).
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If not provided, an automated message will be generated.
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--ff-only
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Refuse to merge and exit with 1 unless the current HEAD is already up to date or the merge can be resolved as a fast-forward.
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--no-ff
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[NOT IMPLEMENTED]
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Create a merge commit even when the merge resolves as a fast-forward.
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--no-commit
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[NOT IMPLEMENTED]
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With --no-commit perform the merge but pretend the merge failed and do not autocommit, to give the user a chance to
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inspect and further tweak the merge result before committing.
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--allow-unrelated-histories
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[NOT IMPLEMENTED]
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By default, git merge command refuses to merge histories that do not share a common ancestor. This option can be
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used to override this safety when merging histories of two projects that started their lives independently.
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DISCUSSION:
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Assume the following history exists and the current branch is "master":
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o---o---o---o---C <topic
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/ /
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---C---B---o---A---o---G <master <HEAD
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Then "%_COMMAND_NAME_% <path> master topic" will replay the changes made on the topic branch since it diverged from master (i.e., A) until its current commit (i.e., C) on top of master, and record the result in a new commit (i.e., M) along with the names of the two parent commits and a log message from the user describing the changes.
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o---o---o---o---C <topic
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/ / \
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---C---B---o---A---o---G---M <HEAD
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Once the merge has been performed successfully HEAD will be updated to the new merge commit.
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`
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‎_examples/merge/main.go

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package main
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import (
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"fmt"
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"os"
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"gopkg.in/src-d/go-git.v4"
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utils "gopkg.in/src-d/go-git.v4/_examples"
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"gopkg.in/src-d/go-git.v4/plumbing"
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"gopkg.in/src-d/go-git.v4/plumbing/object"
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)
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type exitCode int
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const (
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exitCodeNoFastForward utils.ExitCode = 1
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exitCodeFeatureNotImplemented utils.ExitCode = 9
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)
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const (
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cmdDesc = "Performs the merge between two commits, and moves HEAD into the merge commit:"
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helpShortMsg = `
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usage: %_COMMAND_NAME_% <path> <baseCommitRev> <commitRev> [-m <msg>] [--ff-only]
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[--no-ff] [--no-commit] [--allow-unrelated-histories]
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or: %_COMMAND_NAME_% --help
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params:
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<path> Path to the git repository
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<baseCommitRev> Git revision of the commit that will be the base of the merge
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<commitRev> Git revision of the commit that will be merged over the base
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options:
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(no options) Performs the regular merge, as fast-forward if possible
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--ff-only If the merge is not a fast-forward the process exits with 1
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--help Show the full help message of %_COMMAND_NAME_%
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[NOT IMPLEMENTED]
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-m <msg> Uses the passed <msg> for the merge commit message
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--no-ff Create a merge commit even when it could be a fast-forward
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--no-commit Performs the merge in the worktree and do not create a commit
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--allow-unrelated-histories
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Lets the merge to operate with commits not sharing its history
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`
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)
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func main() {
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if len(os.Args) == 1 {
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utils.HelpAndExit(cmdDesc, helpShortMsg)
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}
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if os.Args[1] == "--help" || os.Args[1] == "-h" {
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utils.HelpAndExit(cmdDesc, helpLongMsg)
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}
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if len(os.Args) < 4 {
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utils.WrongSyntaxAndExit(helpShortMsg)
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}
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path := os.Args[1]
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commitRevs := os.Args[2:4]
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mergeOptions := &git.MergeOptions{}
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if len(os.Args) > 4 {
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args := os.Args[4:]
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skipNext := false
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for i, v := range args {
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if skipNext {
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skipNext = false
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continue
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}
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switch v {
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case "--no-ff":
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mergeOptions.NoFF = true
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case "--ff-only":
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mergeOptions.FFOnly = true
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case "--no-commit":
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mergeOptions.NoCommit = true
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case "--allow-unrelated-histories":
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mergeOptions.AllowUnrelated = true
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case "-m":
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if len(args) < i+2 {
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utils.WrongSyntaxAndExit("message not defined, should be -m <msg>")
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}
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mergeOptions.Message = args[i+1]
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skipNext = true
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default:
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utils.WrongSyntaxAndExit(helpShortMsg)
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}
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}
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}
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// Open a git repository from current directory
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repo, err := git.PlainOpen(path)
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utils.ExitIfError(err, utils.ExitCodeCouldNotOpenRepository)
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// Get the hashes of the passed revisions
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var hashes []*plumbing.Hash
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for _, rev := range commitRevs {
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hash, err := repo.ResolveRevision(plumbing.Revision(rev))
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utils.ExitIfError(err, utils.ExitCodeCouldNotParseRevision, rev)
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hashes = append(hashes, hash)
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}
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// Get the commits identified by the passed hashes
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var commits []*object.Commit
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for _, hash := range hashes {
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commit, err := repo.CommitObject(*hash)
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utils.ExitIfError(err, utils.ExitCodeWrongCommitHash, hash.String())
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commits = append(commits, commit)
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}
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commit, err := git.Merge(repo, commits[0], commits[1], mergeOptions)
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switch err {
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case git.ErrSameCommit:
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fmt.Println("Already up to date. Both are the same commit.")
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return
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case git.ErrAlreadyUpToDate:
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fmt.Println("Already up to date.")
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return
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case git.ErrNotImplementedUnrelated,
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git.ErrNotImplementedNoCommit,
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git.ErrNotImplementedNoFF,
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git.ErrNotImplementedMessage:
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utils.ExitIfError(err, exitCodeFeatureNotImplemented, "unimplemented feature")
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}
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utils.ExitIfError(err, utils.ExitCodeExpected, "merge failed")
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utils.PrintCommits(commit)
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}

‎merge.go

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package git
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import (
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"errors"
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"fmt"
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"gopkg.in/src-d/go-git.v4/plumbing/object"
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)
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type strategy int
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const (
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// Fail will cause the merge fail if a conflict is found
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Fail strategy = iota
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// Ours will use the changes from candidate if a conflict is found
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Ours
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// Theirs will use the changes from the base if a conflict is found
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Theirs
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)
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var (
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// ErrSameCommit returned when passed commits are the same
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ErrSameCommit = errors.New("passed commits are the same")
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// ErrAlreadyUpToDate returned when the second is behind first
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ErrAlreadyUpToDate = errors.New("second is behind first")
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// ErrHasConflicts returned when conflicts found
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ErrHasConflicts = errors.New("conflicts found")
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// ErrNoCommonHistory returned when no shared history
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ErrNoCommonHistory = errors.New("no shared history")
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// ErrNonFastForwardUpdate returned when no fast forward was possible
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// defined at worktree.go
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// ErrWorktreeNotClean returned when no clean state in worktree
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// defined at worktree.go
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// ExitCodeUnexpected returned when commit merge is required
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ErrNotImplementedNoFF = errors.New("no fast-forward merge is not implemented")
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// ErrNotImplementedNoCommit returned when no-commit is required
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ErrNotImplementedNoCommit = errors.New("no commit merge is not implemented")
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// ErrNotImplementedUnrelated returned
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ErrNotImplementedUnrelated = errors.New("unrelated merge is not implemented")
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// ErrNotImplementedMessage returned
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ErrNotImplementedMessage = errors.New("custom message is not implemented")
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)
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// MergeOptions describes how a merge should be performed.
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type MergeOptions struct {
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NoFF bool // NoFF when set to true, Merge will always create a merge commit
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FFOnly bool // FFOnly causes the Merge fail if it is not a fast forward
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NoCommit bool // NoCommit leaves the changes in the worktree without commit them
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AllowUnrelated bool // AllowUnrelated performs the merge even with unrelated histories
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Message string // Message text to be used for the message
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}
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// Merge merges the second commit over the first one, and moves `HEAD` to the merge.
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// If `NoCommit` option was passed, the changes required for the merge will be
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// left in the worktree, and the merge commit won't be created.
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// It returns the merge commit, and an error if the HEAD was not moved or
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// when the merge operation could not be done.
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func Merge(
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repo *Repository,
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first *object.Commit,
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second *object.Commit,
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options *MergeOptions,
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) (*object.Commit, error) {
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if options == nil {
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options = &MergeOptions{}
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}
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worktree, err := repo.Worktree()
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if err != nil {
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return nil, err
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}
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status, err := worktree.Status()
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if err != nil {
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return nil, err
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}
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for range status {
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return nil, ErrWorktreeNotClean
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}
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if first.Hash == second.Hash {
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return nil, ErrSameCommit
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}
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ancestors, err := MergeBase(first, second)
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if err != nil {
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return nil, err
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}
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if len(ancestors) == 0 {
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if options.AllowUnrelated {
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return merge(first, second, nil, options.NoCommit, options.Message)
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}
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return nil, ErrNoCommonHistory
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}
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for _, ancestor := range ancestors {
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if ancestor.Hash == first.Hash {
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if options.NoFF {
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// TODO(dpordomingo): there is a special case;
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// if asked with `--no-ff` it should be created an empty merge-commit.
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return nil, ErrNotImplementedNoFF
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}
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return second, nil
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}
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if ancestor.Hash == second.Hash {
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return nil, ErrAlreadyUpToDate
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}
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}
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mergeBase := ancestors[0]
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if options.FFOnly {
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return nil, ErrNonFastForwardUpdate
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}
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return merge(first, second, mergeBase, options.NoCommit, options.Message)
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}
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func merge(
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first, second, mergeBase *object.Commit,
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noCommit bool,
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msg string,
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) (*object.Commit, error) {
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if mergeBase == nil {
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// TODO(dpordomingo): handle --no-commit flag
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return nil, ErrNotImplementedUnrelated
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}
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var trees []*object.Tree
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for _, commit := range []*object.Commit{first, second} {
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tree, err := commit.Tree()
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if err != nil {
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return nil, err
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}
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trees = append(trees, tree)
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}
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changes, err := object.DiffTree(trees[0], trees[1])
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if err != nil {
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return nil, err
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}
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fmt.Println(changes)
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if noCommit {
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// TODO(dpordomingo): handle --no-commit flag
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return nil, ErrNotImplementedNoCommit
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}
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if msg != "" {
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// TODO(dpordomingo): handle -m option
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return nil, ErrNotImplementedMessage
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}
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// TODO(dpordomingo)
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return nil, ErrNotImplementedNoFF
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}

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