1 files changed, 124 insertions, 0 deletions
diff --git a/_examples/merge_base/main.go b/_examples/merge_base/main.go
new file mode 100644
index 0000000..fe6abc6
--- /dev/null
+++ b/_examples/merge_base/main.go
@@ -0,0 +1,124 @@
+package main
+
+import (
+	"os"
+
+	"gopkg.in/src-d/go-git.v4"
+	"gopkg.in/src-d/go-git.v4/plumbing"
+	"gopkg.in/src-d/go-git.v4/plumbing/object"
+)
+
+type exitCode int
+
+const (
+	exitCodeSuccess exitCode = iota
+	exitCodeNotFound
+	exitCodeWrongSyntax
+	exitCodeCouldNotOpenRepository
+	exitCodeCouldNotParseRevision
+	exitCodeUnexpected
+
+	cmdDesc = "Returns the merge-base between two commits:"
+
+	helpShortMsg = `
+  usage: %_COMMAND_NAME_% <path> <commitRev> <commitRev>
+     or: %_COMMAND_NAME_% <path> --independent <commitRev>...
+     or: %_COMMAND_NAME_% <path> --is-ancestor <commitRev> <commitRev>
+     or: %_COMMAND_NAME_% --help
+
+ params:
+    <path>          path to the git repository
+    <commitRev>     git revision as supported by go-git
+
+options:
+    (no options)    lists the best common ancestors of the two passed commits
+    --independent   list commits not reachable from the others
+    --is-ancestor   is the first one ancestor of the other?
+    --help          show the full help message of %_COMMAND_NAME_%
+`
+)
+
+// Command that mimics `git merge-base --all <baseRev> <headRev>`
+// Command that mimics `git merge-base --is-ancestor <baseRev> <headRev>`
+// Command that mimics `git merge-base --independent <commitRev>...`
+func main() {
+	if len(os.Args) == 1 {
+		helpAndExit("Returns the merge-base between two commits:", helpShortMsg, exitCodeSuccess)
+	}
+
+	if os.Args[1] == "--help" || os.Args[1] == "-h" {
+		helpAndExit("Returns the merge-base between two commits:", helpLongMsg, exitCodeSuccess)
+	}
+
+	if len(os.Args) < 4 {
+		helpAndExit("Wrong syntax", helpShortMsg, exitCodeWrongSyntax)
+	}
+
+	path := os.Args[1]
+
+	var modeIndependent, modeAncestor bool
+	var commitRevs []string
+	var res []*object.Commit
+
+	switch os.Args[2] {
+	case "--independent":
+		modeIndependent = true
+		commitRevs = os.Args[3:]
+	case "--is-ancestor":
+		modeAncestor = true
+		commitRevs = os.Args[3:]
+		if len(commitRevs) != 2 {
+			helpAndExit("Wrong syntax", helpShortMsg, exitCodeWrongSyntax)
+		}
+	default:
+		commitRevs = os.Args[2:]
+		if len(commitRevs) != 2 {
+			helpAndExit("Wrong syntax", helpShortMsg, exitCodeWrongSyntax)
+		}
+	}
+
+	// Open a git repository from current directory
+	repo, err := git.PlainOpen(path)
+	checkIfError(err, exitCodeCouldNotOpenRepository, "not in a git repository")
+
+	// Get the hashes of the passed revisions
+	var hashes []*plumbing.Hash
+	for _, rev := range commitRevs {
+		hash, err := repo.ResolveRevision(plumbing.Revision(rev))
+		checkIfError(err, exitCodeCouldNotParseRevision, "could not parse revision '%s'", rev)
+		hashes = append(hashes, hash)
+	}
+
+	// Get the commits identified by the passed hashes
+	var commits []*object.Commit
+	for _, hash := range hashes {
+		commit, err := repo.CommitObject(*hash)
+		checkIfError(err, exitCodeUnexpected, "could not find commit '%s'", hash.String())
+		commits = append(commits, commit)
+	}
+
+	if modeAncestor {
+		isAncestor, err := commits[0].IsAncestor(commits[1])
+		checkIfError(err, exitCodeUnexpected, "could not traverse the repository history")
+
+		if !isAncestor {
+			os.Exit(int(exitCodeNotFound))
+		}
+
+		os.Exit(int(exitCodeSuccess))
+	}
+
+	if modeIndependent {
+		res, err = object.Independents(commits)
+		checkIfError(err, exitCodeUnexpected, "could not traverse the repository history")
+	} else {
+		res, err = commits[0].MergeBase(commits[1])
+		checkIfError(err, exitCodeUnexpected, "could not traverse the repository history")
+
+		if len(res) == 0 {
+			os.Exit(int(exitCodeNotFound))
+		}
+	}
+
+	printCommits(res)
+}