Merge branch 'gl/web'

* gl/web: (46 commits)
  gitweb: Use @diff_opts, default ('M'), as git-diff and git-diff-tree paramete
  gitweb: Remove git_to_hash function
  gitweb: Remove unused git_get_{preceding,following}_references
  gitweb: Fix typo in git_patchset_body
  gitweb: Fix typo in git_difftree_body
  gitweb: blobs defined by non-textual hash ids can be cached
  gitweb: Improve comments about gitweb features configuration
  gitweb: Remove workaround for git-diff bug fixed in f82cd3c
  gitweb: Remove creating directory for temporary files
  gitweb: Remove git_diff_print subroutine
  gitweb: git_blobdiff_plain is git_blobdiff('plain')
  gitweb: Use git-diff-tree or git-diff patch output for blobdiff
  gitweb: Change here-doc back for style consistency in git_blobdiff
  gitweb: Always display link to blobdiff_plain in git_blobdiff
  gitweb: Add invisible hyperlink to from-file/to-file diff header
  gitweb: Parse two-line from-file/to-file diff header in git_patchset_body
  gitweb: Allow for pre-parsed difftree info in git_patchset_body
  gitweb: Add support for hash_parent_base parameter for blobdiffs
  gitweb: Use git_get_name_rev_tags for commitdiff_plain X-Git-Tag: header
  gitweb: Add git_get_rev_name_tags function
  ...