--- a/mercurial/templatefuncs.py	Fri Mar 20 23:30:23 2020 -0400
+++ b/mercurial/templatefuncs.py	Sun Mar 15 15:12:44 2020 +0900
@@ -668,7 +668,7 @@
         else:
             revs = query(raw)
             revsetcache[raw] = revs
-    return templatekw.showrevslist(context, mapping, b"revision", revs)
+    return templateutil.revslist(repo, revs, name=b'revision')
 
 
 @templatefunc(b'rstdoc(text, style)')

--- a/mercurial/templatekw.py	Fri Mar 20 23:30:23 2020 -0400
+++ b/mercurial/templatekw.py	Sun Mar 15 15:12:44 2020 +0900
@@ -873,24 +873,6 @@
     return scmutil.intrev(ctx)
 
 
-def showrevslist(context, mapping, name, revs):
-    """helper to generate a list of revisions in which a mapped template will
-    be evaluated"""
-    repo = context.resource(mapping, b'repo')
-    # revs may be a smartset; don't compute it until f() has to be evaluated
-    def f():
-        srevs = [b'%d' % r for r in revs]
-        return _showcompatlist(context, mapping, name, srevs)
-
-    return _hybrid(
-        f,
-        revs,
-        lambda x: {name: x, b'ctx': repo[x]},
-        pycompat.identity,
-        keytype=int,
-    )
-
-
 @templatekeyword(b'subrepos', requires={b'ctx'})
 def showsubrepos(context, mapping):
     """List of strings. Updated subrepositories in the changeset."""

--- a/mercurial/templater.py	Fri Mar 20 23:30:23 2020 -0400
+++ b/mercurial/templater.py	Sun Mar 15 15:12:44 2020 +0900
@@ -45,6 +45,9 @@
 hybriditem
     represents a scalar printable value, also supports % operator.
 
+revslist
+    represents a list of revision numbers.
+
 mappinggenerator, mappinglist
     represents mappings (i.e. a list of dicts), which may have default
     output format.

--- a/mercurial/templateutil.py	Fri Mar 20 23:30:23 2020 -0400
+++ b/mercurial/templateutil.py	Sun Mar 15 15:12:44 2020 +0900
@@ -15,6 +15,7 @@
 from . import (
     error,
     pycompat,
+    smartset,
     util,
 )
 from .utils import (
@@ -408,6 +409,74 @@
         return _unthunk(context, mapping, self._value)
 
 
+class revslist(wrapped):
+    """Wrapper for a smartset (a list/set of revision numbers)
+
+    If name specified, the revs will be rendered with the old-style list
+    template of the given name by default.
+    """
+
+    def __init__(self, repo, revs, name=None):
+        assert isinstance(revs, smartset.abstractsmartset)
+        self._repo = repo
+        self._revs = revs
+        self._name = name
+
+    def contains(self, context, mapping, item):
+        rev = unwrapinteger(context, mapping, item)
+        return rev in self._revs
+
+    def getmember(self, context, mapping, key):
+        raise error.ParseError(_(b'not a dictionary'))
+
+    def getmin(self, context, mapping):
+        makehybriditem = self._makehybriditemfunc()
+        return makehybriditem(self._revs.min())
+
+    def getmax(self, context, mapping):
+        makehybriditem = self._makehybriditemfunc()
+        return makehybriditem(self._revs.max())
+
+    def filter(self, context, mapping, select):
+        makehybriditem = self._makehybriditemfunc()
+        frevs = self._revs.filter(lambda r: select(makehybriditem(r)))
+        # once filtered, no need to support old-style list template
+        return revslist(self._repo, frevs, name=None)
+
+    def itermaps(self, context):
+        makemap = self._makemapfunc()
+        for r in self._revs:
+            yield makemap(r)
+
+    def _makehybriditemfunc(self):
+        makemap = self._makemapfunc()
+        return lambda r: hybriditem(None, r, r, makemap)
+
+    def _makemapfunc(self):
+        repo = self._repo
+        name = self._name
+        if name:
+            return lambda r: {name: r, b'ctx': repo[r]}
+        else:
+            return lambda r: {b'ctx': repo[r]}
+
+    def join(self, context, mapping, sep):
+        return joinitems(self._revs, sep)
+
+    def show(self, context, mapping):
+        if self._name:
+            srevs = [b'%d' % r for r in self._revs]
+            return _showcompatlist(context, mapping, self._name, srevs)
+        else:
+            return self.join(context, mapping, b' ')
+
+    def tobool(self, context, mapping):
+        return bool(self._revs)
+
+    def tovalue(self, context, mapping):
+        return list(self._revs)
+
+
 class _mappingsequence(wrapped):
     """Wrapper for sequence of template mappings
 

--- a/tests/test-template-functions.t	Fri Mar 20 23:30:23 2020 -0400
+++ b/tests/test-template-functions.t	Sun Mar 15 15:12:44 2020 +0900
@@ -820,6 +820,8 @@
   {"branch": "default"}
   $ hg log -r0 -T '{date|json}\n'
   [0, 0]
+  $ hg log -r0 -T '{revset(":")|json}\n'
+  [0, 1]
 
 Test json filter applied to map result:
 
@@ -1263,6 +1265,28 @@
   5:13207e5a10d9fd28ec424934298e176197f2c67f,
   4:bbe44766e73d5f11ed2177f1838de10c53ef3e74
 
+for historical reasons, revset() supports old-style list template
+
+  $ hg log -T '{revset(":")}\n' -l1 \
+  >        --config templates.start_revisions='"["' \
+  >        --config templates.end_revisions='"]"' \
+  >        --config templates.revision='"{revision}, "' \
+  >        --config templates.last_revision='"{revision}"'
+  [0, 1, 2]
+  $ hg log -T '{revset(":") % " {revision}"}\n' -l1
+   0 1 2
+
+but a filtered one doesn't
+
+  $ hg log -T '{filter(revset(":"), ifeq(rev, 1, "", "y"))}\n' -l1 \
+  >        --config templates.start_revisions='"["' \
+  >        --config templates.end_revisions='"]"' \
+  >        --config templates.revision='"{revision}, "' \
+  >        --config templates.last_revision='"{revision}"'
+  0 2
+  $ hg log -T '{filter(revset(":"), ifeq(rev, 1, "", "y")) % "x{revision}"}\n' -l1
+  xx
+
 %d parameter handling:
 
   $ hg log -T '{revset("%d", rev)}\n' -r'wdir()'
@@ -1318,6 +1342,13 @@
   hg: parse error: invalid argument for revspec
   [255]
 
+Invalid operation on revset()
+
+  $ hg log -T '{get(revset(":"), "foo")}\n'
+  hg: parse error: not a dictionary
+  (get() expects a dict as first argument)
+  [255]
+
 Test files function
 
   $ hg log -T "{rev}\n{join(files('*'), '\n')}\n"
@@ -1568,6 +1599,23 @@
    }
   ]
 
+  $ hg log -T "{revset(':')|cbor}" -R a -l1 | "$PYTHON" "$TESTTMP/decodecbor.py"
+  [
+   [
+    0,
+    1,
+    2,
+    3,
+    4,
+    5,
+    6,
+    7,
+    8,
+    9,
+    10
+   ]
+  ]
+
 json filter should escape HTML tags so that the output can be embedded in hgweb:
 
   $ hg log -T "{'<foo@example.org>'|json}\n" -R a -l1