Number of commits ahead/behind in branch overview (#6695)

* Call Git API to determine divergence of a branch and its base branch

Signed-off-by: Mario Lubenka <mario.lubenka@googlemail.com>

* Show commit divergance in branch list

Signed-off-by: Mario Lubenka <mario.lubenka@googlemail.com>

* Adds missing comment

Signed-off-by: Mario Lubenka <mario.lubenka@googlemail.com>

* Adds test for diverging commits

Signed-off-by: Mario Lubenka <mario.lubenka@googlemail.com>

* Try comparing commits instead of branches

Signed-off-by: Mario Lubenka <mario.lubenka@googlemail.com>

* Removes test as CI can't run it

Signed-off-by: Mario Lubenka <mario.lubenka@googlemail.com>

* Adjusts signature of percentage function to allow providing multiple integers as numerator

Signed-off-by: Mario Lubenka <mario.lubenka@googlemail.com>

* Moves CountDivergingCommits function into repofiles module

Signed-off-by: Mario Lubenka <mario.lubenka@googlemail.com>

3 files changed, 65 insertions, 0 deletions

diff --git a/modules/git/repo.go b/modules/git/repo.go
index f86c4aae5c..8355f8811f 100644
--- a/modules/git/repo.go
+++ b/modules/git/repo.go
@@ -9,9 +9,11 @@ import (
 	"bytes"
 	"container/list"
 	"errors"
+	"fmt"
 	"os"
 	"path"
 	"path/filepath"
+	"strconv"
 	"strings"
 	"time"
 
@@ -306,3 +308,40 @@ func GetLatestCommitTime(repoPath string) (time.Time, error) {
 	commitTime := strings.TrimSpace(stdout)
 	return time.Parse(GitTimeLayout, commitTime)
 }
+
+// DivergeObject represents commit count diverging commits
+type DivergeObject struct {
+	Ahead  int
+	Behind int
+}
+
+func checkDivergence(repoPath string, baseBranch string, targetBranch string) (int, error) {
+	branches := fmt.Sprintf("%s..%s", baseBranch, targetBranch)
+	cmd := NewCommand("rev-list", "--count", branches)
+	stdout, err := cmd.RunInDir(repoPath)
+	if err != nil {
+		return -1, err
+	}
+	outInteger, errInteger := strconv.Atoi(strings.Trim(stdout, "\n"))
+	if errInteger != nil {
+		return -1, errInteger
+	}
+	return outInteger, nil
+}
+
+// GetDivergingCommits returns the number of commits a targetBranch is ahead or behind a baseBranch
+func GetDivergingCommits(repoPath string, baseBranch string, targetBranch string) (DivergeObject, error) {
+	// $(git rev-list --count master..feature) commits ahead of master
+	ahead, errorAhead := checkDivergence(repoPath, baseBranch, targetBranch)
+	if errorAhead != nil {
+		return DivergeObject{}, errorAhead
+	}
+
+	// $(git rev-list --count feature..master) commits behind master
+	behind, errorBehind := checkDivergence(repoPath, targetBranch, baseBranch)
+	if errorBehind != nil {
+		return DivergeObject{}, errorBehind
+	}
+
+	return DivergeObject{ahead, behind}, nil
+}
diff --git a/modules/repofiles/commit.go b/modules/repofiles/commit.go
new file mode 100644
index 0000000000..371e6cf3ab
--- /dev/null
+++ b/modules/repofiles/commit.go
@@ -0,0 +1,19 @@
+// Copyright 2019 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 repofiles
+
+import (
+	"code.gitea.io/gitea/models"
+	"code.gitea.io/gitea/modules/git"
+)
+
+// CountDivergingCommits determines how many commits a branch is ahead or behind the repository's base branch
+func CountDivergingCommits(repo *models.Repository, branch string) (*git.DivergeObject, error) {
+	divergence, err := git.GetDivergingCommits(repo.RepoPath(), repo.DefaultBranch, branch)
+	if err != nil {
+		return nil, err
+	}
+	return &divergence, nil
+}
diff --git a/modules/templates/helper.go b/modules/templates/helper.go
index 6d964e88a5..3176684d82 100644
--- a/modules/templates/helper.go
+++ b/modules/templates/helper.go
@@ -223,6 +223,13 @@ func NewFuncMap() []template.FuncMap {
 			}
 			return dict, nil
 		},
+		"percentage": func(n int, values ...int) float32 {
+			var sum = 0
+			for i := 0; i < len(values); i++ {
+				sum += values[i]
+			}
+			return float32(n) * 100 / float32(sum)
+		},
 	}}
 }