lfs: add the '{lfsattrs}' template keyword to '{lfs_files}'

This provides access to the metadata dictionary contained within the tracked
pointer file.  The OID is probably the most important attribute, and has its own
keyword.  But we might as well have this for completeness.

I liked {pointer} better, but couldn't make it work with the singular/plural
forms.

hgext/lfs/__init__.py

@@ -97,6 +97,7 b' from mercurial import ('
     scmutil,
     templatekw,
     upgrade,
+    util,
     vfs as vfsmod,
     wireproto,
 )
@@ -311,9 +312,16 b' def lfsfiles(repo, ctx, **args):'
     pointers = wrapper.pointersfromctx(ctx) # {path: pointer}
     files = sorted(pointers.keys())
 
+    def lfsattrs(v):
+        # In the file spec, version is first and the other keys are sorted.
+        sortkeyfunc = lambda x: (x[0] != 'version', x)
+        items = sorted(pointers[v].iteritems(), key=sortkeyfunc)
+        return util.sortdict(items)
+
     makemap = lambda v: {
         'file': v,
         'oid': pointers[v].oid(),
+        'lfsattrs': templatekw.hybriddict(lfsattrs(v)),
     }
 
     # TODO: make the separator ', '?

tests/test-lfs.t

@@ -865,6 +865,17 b" there's no 'lfs' destination repo requir"
   oid sha256:5bb8341bee63b3649f222b2215bde37322bea075a30575aa685d8f8d21c77024
   size 29
   x-is-binary 0
+  $ hg --cwd convert_lfs log -r 0 -T "{lfs_files % '{lfsattrs % '{key}={value}\n'}'}"
+  version=https://git-lfs.github.com/spec/v1
+  oid=sha256:5bb8341bee63b3649f222b2215bde37322bea075a30575aa685d8f8d21c77024
+  size=29
+  x-is-binary=0
+  $ hg --cwd convert_lfs log -r 0 \
+  >    -T '{lfs_files % "{get(lfsattrs, "oid")}\n"}{lfs_files % "{lfsattrs.oid}\n"}'
+  sha256:5bb8341bee63b3649f222b2215bde37322bea075a30575aa685d8f8d21c77024
+  sha256:5bb8341bee63b3649f222b2215bde37322bea075a30575aa685d8f8d21c77024
+  $ hg --cwd convert_lfs log -r 0 -T '{lfs_files % "{lfsattrs}\n"}'
+  version=https://git-lfs.github.com/spec/v1 oid=sha256:5bb8341bee63b3649f222b2215bde37322bea075a30575aa685d8f8d21c77024 size=29 x-is-binary=0
   $ hg --cwd convert_lfs \
   >     log -r 'all()' -T '{rev}: {lfs_files % "{file}: {oid}\n"}'
   0: a1: 5bb8341bee63b3649f222b2215bde37322bea075a30575aa685d8f8d21c77024