Keeping consistent between UI and API about combined commit status state and fix some bugs (#34562)

Extract from #34531 

## Move Commit status state to a standalone package

Move the state from `structs` to `commitstatus` package. It also
introduce `CommitStatusStates` so that the combine function could be
used from UI and API logic.

## Combined commit status Changed

This PR will follow Github's combined commit status. Before this PR,
every commit status could be a combined one.
According to
https://docs.github.com/en/rest/commits/statuses?apiVersion=2022-11-28#get-the-combined-status-for-a-specific-reference
> Additionally, a combined state is returned. The state is one of:
> failure if any of the contexts report as error or failure
> pending if there are no statuses or a context is pending
> success if the latest status for all contexts is success

This PR will follow that rule and remove the `NoBetterThan` logic. This
also fixes the inconsistent between UI and API. In the API convert
package, it has implemented this which is different from the UI. It also
fixed the missing `URL` and `CommitURL` in the API.

## `CalcCommitStatus` return nil if there is no commit statuses

The behavior of `CalcCommitStatus` is changed. If the parameter commit
statuses is empty, it will return nil. The reference places should check
the returned value themselves.

1 files changed, 201 insertions, 0 deletions

diff --git a/modules/commitstatus/commit_status_test.go b/modules/commitstatus/commit_status_test.go
new file mode 100644
index 0000000000..10d8f20aa4
--- /dev/null
+++ b/modules/commitstatus/commit_status_test.go
@@ -0,0 +1,201 @@
+// Copyright 2025 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package commitstatus
+
+import "testing"
+
+func TestCombine(t *testing.T) {
+	tests := []struct {
+		name     string
+		states   CommitStatusStates
+		expected CommitStatusState
+	}{
+		// 0 states
+		{
+			name:     "empty",
+			states:   CommitStatusStates{},
+			expected: CommitStatusPending,
+		},
+		// 1 state
+		{
+			name:     "pending",
+			states:   CommitStatusStates{CommitStatusPending},
+			expected: CommitStatusPending,
+		},
+		{
+			name:     "success",
+			states:   CommitStatusStates{CommitStatusSuccess},
+			expected: CommitStatusSuccess,
+		},
+		{
+			name:     "error",
+			states:   CommitStatusStates{CommitStatusError},
+			expected: CommitStatusFailure,
+		},
+		{
+			name:     "failure",
+			states:   CommitStatusStates{CommitStatusFailure},
+			expected: CommitStatusFailure,
+		},
+		{
+			name:     "warning",
+			states:   CommitStatusStates{CommitStatusWarning},
+			expected: CommitStatusSuccess,
+		},
+		// 2 states
+		{
+			name:     "pending and success",
+			states:   CommitStatusStates{CommitStatusPending, CommitStatusSuccess},
+			expected: CommitStatusPending,
+		},
+		{
+			name:     "pending and error",
+			states:   CommitStatusStates{CommitStatusPending, CommitStatusError},
+			expected: CommitStatusFailure,
+		},
+		{
+			name:     "pending and failure",
+			states:   CommitStatusStates{CommitStatusPending, CommitStatusFailure},
+			expected: CommitStatusFailure,
+		},
+		{
+			name:     "pending and warning",
+			states:   CommitStatusStates{CommitStatusPending, CommitStatusWarning},
+			expected: CommitStatusPending,
+		},
+		{
+			name:     "success and error",
+			states:   CommitStatusStates{CommitStatusSuccess, CommitStatusError},
+			expected: CommitStatusFailure,
+		},
+		{
+			name:     "success and failure",
+			states:   CommitStatusStates{CommitStatusSuccess, CommitStatusFailure},
+			expected: CommitStatusFailure,
+		},
+		{
+			name:     "success and warning",
+			states:   CommitStatusStates{CommitStatusSuccess, CommitStatusWarning},
+			expected: CommitStatusSuccess,
+		},
+		{
+			name:     "error and failure",
+			states:   CommitStatusStates{CommitStatusError, CommitStatusFailure},
+			expected: CommitStatusFailure,
+		},
+		{
+			name:     "error and warning",
+			states:   CommitStatusStates{CommitStatusError, CommitStatusWarning},
+			expected: CommitStatusFailure,
+		},
+		{
+			name:     "failure and warning",
+			states:   CommitStatusStates{CommitStatusFailure, CommitStatusWarning},
+			expected: CommitStatusFailure,
+		},
+		// 3 states
+		{
+			name:     "pending, success and warning",
+			states:   CommitStatusStates{CommitStatusPending, CommitStatusSuccess, CommitStatusWarning},
+			expected: CommitStatusPending,
+		},
+		{
+			name:     "pending, success and error",
+			states:   CommitStatusStates{CommitStatusPending, CommitStatusSuccess, CommitStatusError},
+			expected: CommitStatusFailure,
+		},
+		{
+			name:     "pending, success and failure",
+			states:   CommitStatusStates{CommitStatusPending, CommitStatusSuccess, CommitStatusFailure},
+			expected: CommitStatusFailure,
+		},
+		{
+			name:     "pending, error and failure",
+			states:   CommitStatusStates{CommitStatusPending, CommitStatusError, CommitStatusFailure},
+			expected: CommitStatusFailure,
+		},
+		{
+			name:     "success, error and warning",
+			states:   CommitStatusStates{CommitStatusSuccess, CommitStatusError, CommitStatusWarning},
+			expected: CommitStatusFailure,
+		},
+		{
+			name:     "success, failure and warning",
+			states:   CommitStatusStates{CommitStatusSuccess, CommitStatusFailure, CommitStatusWarning},
+			expected: CommitStatusFailure,
+		},
+		{
+			name:     "error, failure and warning",
+			states:   CommitStatusStates{CommitStatusError, CommitStatusFailure, CommitStatusWarning},
+			expected: CommitStatusFailure,
+		},
+		{
+			name:     "success, warning and skipped",
+			states:   CommitStatusStates{CommitStatusSuccess, CommitStatusWarning, CommitStatusSkipped},
+			expected: CommitStatusSuccess,
+		},
+		// All success
+		{
+			name:     "all success",
+			states:   CommitStatusStates{CommitStatusSuccess, CommitStatusSuccess, CommitStatusSuccess},
+			expected: CommitStatusSuccess,
+		},
+		// All pending
+		{
+			name:     "all pending",
+			states:   CommitStatusStates{CommitStatusPending, CommitStatusPending, CommitStatusPending},
+			expected: CommitStatusPending,
+		},
+		{
+			name:     "all skipped",
+			states:   CommitStatusStates{CommitStatusSkipped, CommitStatusSkipped, CommitStatusSkipped},
+			expected: CommitStatusSuccess,
+		},
+		// 4 states
+		{
+			name:     "pending, success, error and warning",
+			states:   CommitStatusStates{CommitStatusPending, CommitStatusSuccess, CommitStatusError, CommitStatusWarning},
+			expected: CommitStatusFailure,
+		},
+		{
+			name:     "pending, success, failure and warning",
+			states:   CommitStatusStates{CommitStatusPending, CommitStatusSuccess, CommitStatusFailure, CommitStatusWarning},
+			expected: CommitStatusFailure,
+		},
+		{
+			name:     "pending, error, failure and warning",
+			states:   CommitStatusStates{CommitStatusPending, CommitStatusError, CommitStatusFailure, CommitStatusWarning},
+			expected: CommitStatusFailure,
+		},
+		{
+			name:     "success, error, failure and warning",
+			states:   CommitStatusStates{CommitStatusSuccess, CommitStatusError, CommitStatusFailure, CommitStatusWarning},
+			expected: CommitStatusFailure,
+		},
+		{
+			name:     "mixed states",
+			states:   CommitStatusStates{CommitStatusPending, CommitStatusSuccess, CommitStatusError, CommitStatusWarning},
+			expected: CommitStatusFailure,
+		},
+		{
+			name:     "mixed states with all success",
+			states:   CommitStatusStates{CommitStatusSuccess, CommitStatusSuccess, CommitStatusPending, CommitStatusWarning},
+			expected: CommitStatusPending,
+		},
+		{
+			name:     "all success with warning",
+			states:   CommitStatusStates{CommitStatusSuccess, CommitStatusSuccess, CommitStatusSuccess, CommitStatusWarning},
+			expected: CommitStatusSuccess,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			result := tt.states.Combine()
+			if result != tt.expected {
+				t.Errorf("expected %v, got %v", tt.expected, result)
+			}
+		})
+	}
+}