hooks: add a 'txnabort' hook

This hook will be called whenever a transaction is aborted. This will make it
easy for people to clean up temporary content they may have created during a
transaction.

mercurial/help/config.txt

@@ -833,6 +833,10 b' variables it is passed are listed with n'
   after the lock is released. see ``pretxnclose`` docs for details about
   available variables.
 
+``txnabort``
+  Run when a transaction is aborted. see ``pretxnclose`` docs for details about
+  available variables.
+
 ``pretxnchangegroup``
   Run after a changegroup has been added via push, pull or unbundle,
   but before the transaction has been committed. Changegroup is

mercurial/localrepo.py

@@ -975,6 +975,12 b' class localrepository(object):'
                                **tr2.hookargs)
             reporef()._afterlock(hook)
         tr.addfinalize('txnclose-hook', txnclosehook)
+        def txnaborthook(tr2):
+            """To be run if transaction is aborted
+            """
+            reporef().hook('txnabort', throw=False, txnname=desc,
+                           **tr2.hookargs)
+        tr.addabort('txnabort-hook', txnaborthook)
         self._transref = weakref.ref(tr)
         return tr
 

tests/test-hook.t

@@ -15,6 +15,7 b' commit hooks can see env vars'
   > pretxnopen = sh -c "HG_LOCAL= HG_TAG= python \"$TESTDIR/printenv.py\" pretxnopen"
   > pretxnclose = sh -c "HG_LOCAL= HG_TAG= python \"$TESTDIR/printenv.py\" pretxnclose"
   > txnclose = sh -c "HG_LOCAL= HG_TAG= python \"$TESTDIR/printenv.py\" txnclose"
+  > txnabort = sh -c "HG_LOCAL= HG_TAG= python \"$TESTDIR/printenv.py\" txnabort"
   > EOF
   $ echo a > a
   $ hg add a
@@ -161,6 +162,7 b' more there after'
   5:6f611f8018c1
   pretxncommit.forbid hook: HG_NODE=6f611f8018c10e827fee6bd2bc807f937e761567 HG_PARENT1=539e4b31b6dc99b3cfbaa6b53cbc1c1f9a1e3a10 HG_PENDING=$TESTTMP/a
   transaction abort!
+  txnabort hook: HG_TXNID=TXN:* HG_TXNNAME=commit (glob)
   rollback completed
   abort: pretxncommit.forbid1 hook exited with status 1
   [255]