add new link command to link to another issue

README

@@ -99,6 +99,13 @@ Apply patched atteched to issue 9999.::
 
   git redmine issue apply --issue 9999
 
+link
+----
+
+  git redmine link 9999
+
+Link current branch issue to issue 9999.
+
 merge-and-push
 ..............
 

git_redmine.py

@@ -344,6 +344,28 @@ def new(ctx, reference):
         ctx.invoke(take, issue_number=issue.id, reference=reference)
 
 
+@issue.command()
+@click.argument('issue', type=int)
+def link(issue):
+    '''Create link with another issue'''
+    api = get_redmine_api()
+    current_issue = get_issue()
+    try:
+        target_issue = api.issue.get(issue)
+    except Exception:
+        raise click.UsageError(
+            'Cannot find issue %s' % issue)
+    if len(api.issue_relation.filter(issue_id=current_issue.id, issue_to_id=target_issue.id)):
+        click.echo(click.style('Already linked.', fg='green'))
+        return
+    if click.confirm(f'Link issue {current_issue.id } - « {current_issue.subject} » to {target_issue.id} - « {target_issue.subject} »', default=False, abort=True):
+        api.issue_relation.create(
+            issue_id=current_issue.id,
+            issue_to_id=target_issue.id,
+            relation_type='relates')
+        click.echo(click.style('Linked.', fg='green'))
+
+
 class MyProgressPrinter(git.RemoteProgress):
     def update(self, op_code, cur_count, max_count=None, message=''):
         print(op_code, cur_count, max_count, cur_count / (max_count or 100.0), message or "NO MESSAGE")