scm: git: recovery and improve comments of fetching from 1.1 about harmful influence that git does not have the revision number (#9472)

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/trunk@7658 e93f8b46-1217-0410-a6f0-8f06a7374b81

1 files changed, 11 insertions, 0 deletions

diff --git a/app/models/repository/git.rb b/app/models/repository/git.rb
index a834a765a..be307a5be 100644
--- a/app/models/repository/git.rb
+++ b/app/models/repository/git.rb
@@ -95,6 +95,17 @@ class Repository::Git < Repository
                 options = {:report_last_commit => extra_report_last_commit})
   end
 
+  # With SCMs that have a sequential commit numbering,
+  # such as Subversion and Mercurial,
+  # Redmine is able to be clever and only fetch changesets
+  # going forward from the most recent one it knows about.
+  # 
+  # However, Git does not have a sequential commit numbering.
+  #
+  # In order to fetch only new adding revisions,
+  # Redmine need to parse revisions per branch.
+  # Branch "last_scmid" is for this requirement.
+  #
   # In Git and Mercurial, revisions are not in date order.
   # Redmine Mercurial fixed issues.
   #    * Redmine Takes Too Long On Large Mercurial Repository