changeset 37271:0194dac77c93

scmutil: add method for looking up a context given a revision symbol

changectx's constructor currently supports a mix if inputs:

  * integer revnums
  * binary nodeids
  * '.', 'tip', 'null'
  * stringified revnums
  * namespaced identifiers (e.g. bookmarks and tags)
  * hex nodeids
  * partial hex nodeids

The first two are always internal [1]. The other five can be specified
by the user. The third type ('.', 'tip', 'null') often comes from
either the user or internal callers. We probably have some internal
callers that pass hex nodeids too, perhaps even partial ones
(histedit?). There are only a few callers that pass user-supplied
strings: revsets.stringset, peer.lookup, webutil.changeidctx, and
maybe one or two more.

Supporting this mix of things in the constructor is convenient, but a
bit strange, IMO. For example, if repo[node] is given a node that's
not in the repo, it will first check if it's bookmark etc before
raising an exception. Of course, the risk of it being a bookmark is
extremely small, but it just feels ugly.

Also, a problem with having this code in the constructor (whether it
supports a mix of types or not) is that it's harder to override (I'd
like to override it, and that's how this series started).

This patch starts moving out the handling of user-supplied strings by
introducing scmutil.revsymbol(). So far, that just checks that the
input is indeed a string, and then delegates to repo[symbol]. The
patch also calls it from revsets.stringset to prove that it works.

 [1] Well, you probably can enter a 20-byte binary nodeid on the
     command line, but I don't think we should care to preserve
     support for that.

Differential Revision: https://phab.mercurial-scm.org/D3024

--- a/mercurial/revset.py	Mon Apr 02 23:52:43 2018 -0700
+++ b/mercurial/revset.py	Mon Apr 02 16:18:33 2018 -0700
@@ -118,7 +118,7 @@
 def stringset(repo, subset, x, order):
     if not x:
         raise error.ParseError(_("empty string is not a valid revision"))
-    x = scmutil.intrev(repo[x])
+    x = scmutil.intrev(scmutil.revsymbol(repo, x))
     if (x in subset
         or x == node.nullrev and isinstance(subset, fullreposet)):
         return baseset([x])

--- a/mercurial/scmutil.py	Mon Apr 02 23:52:43 2018 -0700
+++ b/mercurial/scmutil.py	Mon Apr 02 16:18:33 2018 -0700
@@ -433,6 +433,19 @@
         hexfunc = short
     return '%d:%s' % (rev, hexfunc(node))
 
+def revsymbol(repo, symbol):
+    """Returns a context given a single revision symbol (as string).
+
+    This is similar to revsingle(), but accepts only a single revision symbol,
+    i.e. things like ".", "tip", "1234", "deadbeef", "my-bookmark" work, but
+    not "max(public())".
+    """
+    if not isinstance(symbol, bytes):
+        msg = ("symbol (%s of type %s) was not a string, did you mean "
+               "repo[symbol]?" % (symbol, type(symbol)))
+        raise error.ProgrammingError(msg)
+    return repo[symbol]
+
 def revsingle(repo, revspec, default='.', localalias=None):
     if not revspec and revspec != 0:
         return repo[default]