commitctx: stop using weakref proxy for transaction

This weakref proxy was introduced in 2007 by 30d4d8985dd8.

If I understand it correctly, the logic at that time was relying on the
transaction destructor, triggered at garbage collection time to rollback failed
transaction. passing the object to sub function directly mean it would live in
the function scope and be trapped in the traceback on exception, leading to the
transaction rollback too late in some case.

Modern transaction usage use explicit opening and closing of transaction and no
longer rely on some internal reference counting details. So this weakref proxy
is no longer necessary. Absolutely no test are affected when we drop it.

mercurial/commit.py

@@ -6,7 +6,6 b''
 from __future__ import absolute_import
 
 import errno
-import weakref
 
 from .i18n import _
 from .node import (
@@ -62,8 +61,6 b' def commitctx(repo, ctx, error=False, or'
         p2copies = ctx.p2copies()
     filesadded, filesremoved = None, None
     with repo.lock(), repo.transaction(b"commit") as tr:
-        trp = weakref.proxy(tr)
-
         if ctx.manifestnode():
             # reuse an existing manifest revision
             repo.ui.debug(b'reusing known manifest\n')
@@ -102,7 +99,7 b' def commitctx(repo, ctx, error=False, or'
                     else:
                         added.append(f)
                         m[f], is_touched = _filecommit(
-                            repo, fctx, m1, m2, linkrev, trp, writefilecopymeta,
+                            repo, fctx, m1, m2, linkrev, tr, writefilecopymeta,
                         )
                         if is_touched:
                             touched.append(f)
@@ -156,7 +153,7 b' def commitctx(repo, ctx, error=False, or'
                 # case where the merge has files outside of the narrowspec,
                 # so this is safe.
                 mn = mctx.write(
-                    trp,
+                    tr,
                     linkrev,
                     p1.manifestnode(),
                     p2.manifestnode(),
@@ -191,7 +188,7 b' def commitctx(repo, ctx, error=False, or'
             mn,
             files,
             ctx.description(),
-            trp,
+            tr,
             p1.node(),
             p2.node(),
             user,