--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mercurial/tags.py	Thu Jul 16 10:39:41 2009 -0400
@@ -0,0 +1,122 @@
+# tags.py - read tag info from local repository
+#
+# Copyright 2009 Matt Mackall <mpm@selenic.com>
+# Copyright 2009 Greg Ward <greg@gerg.ca>
+#
+# This software may be used and distributed according to the terms of the
+# GNU General Public License version 2, incorporated herein by reference.
+
+# Currently this module only deals with reading tags.  Soon it will grow
+# support for caching tag info.  Eventually, it could take care of
+# updating (adding/removing/moving) tags too.
+
+from node import bin, hex
+from i18n import _
+import encoding
+import error
+
+def findglobaltags(ui, repo, alltags, tagtypes):
+    '''Find global tags in repo by reading .hgtags from every head that
+    has a distinct version of it.  Updates the dicts alltags, tagtypes
+    in place: alltags maps tag name to (node, hist) pair (see _readtags()
+    below), and tagtypes maps tag name to tag type ('global' in this
+    case).'''
+
+    seen = set()
+    fctx = None
+    ctxs = []                       # list of filectx
+    for node in repo.heads():
+        try:
+            fnode = repo[node].filenode('.hgtags')
+        except error.LookupError:
+            continue
+        if fnode not in seen:
+            seen.add(fnode)
+            if not fctx:
+                fctx = repo.filectx('.hgtags', fileid=fnode)
+            else:
+                fctx = fctx.filectx(fnode)
+            ctxs.append(fctx)
+
+    # read the tags file from each head, ending with the tip
+    for fctx in reversed(ctxs):
+        filetags = _readtags(
+            ui, repo, fctx.data().splitlines(), fctx)
+        _updatetags(filetags, "global", alltags, tagtypes)
+
+def readlocaltags(ui, repo, alltags, tagtypes):
+    '''Read local tags in repo.  Update alltags and tagtypes.'''
+    try:
+        data = encoding.fromlocal(repo.opener("localtags").read())
+        # localtags are stored in the local character set
+        # while the internal tag table is stored in UTF-8
+        filetags = _readtags(
+            ui, repo, data.splitlines(), "localtags")
+        _updatetags(filetags, "local", alltags, tagtypes)
+    except IOError:
+        pass
+
+def _readtags(ui, repo, lines, fn):
+    '''Read tag definitions from a file (or any source of lines).
+    Return a mapping from tag name to (node, hist): node is the node id
+    from the last line read for that name, and hist is the list of node
+    ids previously associated with it (in file order).  All node ids are
+    binary, not hex.'''
+
+    filetags = {}               # map tag name to (node, hist)
+    count = 0
+
+    def warn(msg):
+        ui.warn(_("%s, line %s: %s\n") % (fn, count, msg))
+
+    for line in lines:
+        count += 1
+        if not line:
+            continue
+        try:
+            (nodehex, name) = line.split(" ", 1)
+        except ValueError:
+            warn(_("cannot parse entry"))
+            continue
+        name = encoding.tolocal(name.strip()) # stored in UTF-8
+        try:
+            nodebin = bin(nodehex)
+        except TypeError:
+            warn(_("node '%s' is not well formed") % nodehex)
+            continue
+        if nodebin not in repo.changelog.nodemap:
+            # silently ignore as pull -r might cause this
+            continue
+
+        # update filetags
+        hist = []
+        if name in filetags:
+            n, hist = filetags[name]
+            hist.append(n)
+        filetags[name] = (nodebin, hist)
+    return filetags
+
+def _updatetags(filetags, tagtype, alltags, tagtypes):
+    '''Incorporate the tag info read from one file into the two
+    dictionaries, alltags and tagtypes, that contain all tag
+    info (global across all heads plus local).'''
+
+    for name, nodehist in filetags.iteritems():
+        if name not in alltags:
+            alltags[name] = nodehist
+            tagtypes[name] = tagtype
+            continue
+
+        # we prefer alltags[name] if:
+        #  it supercedes us OR
+        #  mutual supercedes and it has a higher rank
+        # otherwise we win because we're tip-most
+        anode, ahist = nodehist
+        bnode, bhist = alltags[name]
+        if (bnode != anode and anode in bhist and
+            (bnode not in ahist or len(bhist) > len(ahist))):
+            anode = bnode
+        ahist.extend([n for n in bhist if n not in ahist])
+        alltags[name] = anode, ahist
+        tagtypes[name] = tagtype
+