diff --git a/mercurial/util.py b/mercurial/util.py
--- a/mercurial/util.py
+++ b/mercurial/util.py
@@ -386,6 +386,10 @@ def system(cmd, environ={}, cwd=None, on
 
     if out is specified, it is assumed to be a file-like object that has a
     write() method. stdout and stderr will be redirected to out.'''
+    try:
+        sys.stdout.flush()
+    except Exception:
+        pass
     def py2shell(val):
         'convert python object into string that is useful to shell'
         if val is None or val is False:
diff --git a/tests/test-bundle.t b/tests/test-bundle.t
--- a/tests/test-bundle.t
+++ b/tests/test-bundle.t
@@ -204,13 +204,13 @@ doesn't work (yet ?)
 hg -R bundle://../full.hg verify
 
   $ hg pull bundle://../full.hg
-  changegroup hook: HG_NODE=f9ee2f85a263049e9ae6d37a0e67e96194ffb735 HG_SOURCE=pull HG_URL=bundle:../full.hg 
   pulling from bundle://../full.hg
   requesting all changes
   adding changesets
   adding manifests
   adding file changes
   added 9 changesets with 7 changes to 4 files (+1 heads)
+  changegroup hook: HG_NODE=f9ee2f85a263049e9ae6d37a0e67e96194ffb735 HG_SOURCE=pull HG_URL=bundle:../full.hg 
   (run 'hg heads' to see heads, 'hg merge' to merge)
 
 Rollback empty
@@ -227,13 +227,13 @@ Log -R bundle:empty+full.hg
 Pull full.hg into empty again (using -R; with hook)
 
   $ hg -R empty pull full.hg
-  changegroup hook: HG_NODE=f9ee2f85a263049e9ae6d37a0e67e96194ffb735 HG_SOURCE=pull HG_URL=bundle:empty+full.hg 
   pulling from full.hg
   requesting all changes
   adding changesets
   adding manifests
   adding file changes
   added 9 changesets with 7 changes to 4 files (+1 heads)
+  changegroup hook: HG_NODE=f9ee2f85a263049e9ae6d37a0e67e96194ffb735 HG_SOURCE=pull HG_URL=bundle:empty+full.hg 
   (run 'hg heads' to see heads, 'hg merge' to merge)
 
 Create partial clones
diff --git a/tests/test-filebranch.t b/tests/test-filebranch.t
--- a/tests/test-filebranch.t
+++ b/tests/test-filebranch.t
@@ -55,10 +55,10 @@ Merging:
   (run 'hg heads' to see heads, 'hg merge' to merge)
 
   $ hg merge -v
-  merging for foo
   resolving manifests
   getting bar
   merging foo
+  merging for foo
   1 files updated, 1 files merged, 0 files removed, 0 files unresolved
   (branch merge, don't forget to commit)
 
diff --git a/tests/test-hook.t b/tests/test-hook.t
--- a/tests/test-hook.t
+++ b/tests/test-hook.t
@@ -76,17 +76,17 @@ test generic hooks
 
   $ cd ../b
   $ hg pull ../a
+  pulling from ../a
+  searching for changes
   prechangegroup hook: HG_SOURCE=pull HG_URL=file:$TESTTMP/a 
+  adding changesets
+  adding manifests
+  adding file changes
+  added 3 changesets with 2 changes to 2 files
   changegroup hook: HG_NODE=ab228980c14deea8b9555d91c9581127383e40fd HG_SOURCE=pull HG_URL=file:$TESTTMP/a 
   incoming hook: HG_NODE=ab228980c14deea8b9555d91c9581127383e40fd HG_SOURCE=pull HG_URL=file:$TESTTMP/a 
   incoming hook: HG_NODE=ee9deb46ab31e4cc3310f3cf0c3d668e4d8fffc2 HG_SOURCE=pull HG_URL=file:$TESTTMP/a 
   incoming hook: HG_NODE=07f3376c1e655977439df2a814e3cc14b27abac2 HG_SOURCE=pull HG_URL=file:$TESTTMP/a 
-  pulling from ../a
-  searching for changes
-  adding changesets
-  adding manifests
-  adding file changes
-  added 3 changesets with 2 changes to 2 files
   (run 'hg update' to get a working copy)
 
 tag hooks can see env vars
@@ -176,9 +176,9 @@ prechangegroup hook can prevent incoming
   $ echo '[hooks]' > .hg/hgrc
   $ echo 'prechangegroup.forbid = python "$TESTDIR"/printenv.py prechangegroup.forbid 1' >> .hg/hgrc
   $ hg pull ../a
-  prechangegroup.forbid hook: HG_SOURCE=pull HG_URL=file:$TESTTMP/a 
   pulling from ../a
   searching for changes
+  prechangegroup.forbid hook: HG_SOURCE=pull HG_URL=file:$TESTTMP/a 
   abort: prechangegroup.forbid hook exited with status 1
   [255]
 
@@ -189,14 +189,14 @@ incoming changes no longer there after
   $ echo 'pretxnchangegroup.forbid0 = hg tip -q' >> .hg/hgrc
   $ echo 'pretxnchangegroup.forbid1 = python "$TESTDIR"/printenv.py pretxnchangegroup.forbid 1' >> .hg/hgrc
   $ hg pull ../a
-  4:539e4b31b6dc
-  pretxnchangegroup.forbid hook: HG_NODE=539e4b31b6dc99b3cfbaa6b53cbc1c1f9a1e3a10 HG_PENDING=$TESTTMP/b HG_SOURCE=pull HG_URL=file:$TESTTMP/a 
   pulling from ../a
   searching for changes
   adding changesets
   adding manifests
   adding file changes
   added 1 changesets with 1 changes to 1 files
+  4:539e4b31b6dc
+  pretxnchangegroup.forbid hook: HG_NODE=539e4b31b6dc99b3cfbaa6b53cbc1c1f9a1e3a10 HG_PENDING=$TESTTMP/b HG_SOURCE=pull HG_URL=file:$TESTTMP/a 
   transaction abort!
   rollback completed
   abort: pretxnchangegroup.forbid1 hook exited with status 1
@@ -211,11 +211,11 @@ outgoing hooks can see env vars
   $ echo 'preoutgoing = python "$TESTDIR"/printenv.py preoutgoing' >> ../a/.hg/hgrc
   $ echo 'outgoing = python "$TESTDIR"/printenv.py outgoing' >> ../a/.hg/hgrc
   $ hg pull ../a
-  preoutgoing hook: HG_SOURCE=pull 
-  outgoing hook: HG_NODE=539e4b31b6dc99b3cfbaa6b53cbc1c1f9a1e3a10 HG_SOURCE=pull 
   pulling from ../a
   searching for changes
+  preoutgoing hook: HG_SOURCE=pull 
   adding changesets
+  outgoing hook: HG_NODE=539e4b31b6dc99b3cfbaa6b53cbc1c1f9a1e3a10 HG_SOURCE=pull 
   adding manifests
   adding file changes
   added 1 changesets with 1 changes to 1 files
@@ -227,10 +227,10 @@ preoutgoing hook can prevent outgoing ch
 
   $ echo 'preoutgoing.forbid = python "$TESTDIR"/printenv.py preoutgoing.forbid 1' >> ../a/.hg/hgrc
   $ hg pull ../a
+  pulling from ../a
+  searching for changes
   preoutgoing hook: HG_SOURCE=pull 
   preoutgoing.forbid hook: HG_SOURCE=pull 
-  pulling from ../a
-  searching for changes
   abort: preoutgoing.forbid hook exited with status 1
   [255]
 
diff --git a/tests/test-http.t b/tests/test-http.t
--- a/tests/test-http.t
+++ b/tests/test-http.t
@@ -76,12 +76,12 @@ pull
   $ echo '[hooks]' >> .hg/hgrc
   $ echo 'changegroup = python "$TESTDIR"/printenv.py changegroup' >> .hg/hgrc
   $ hg pull
-  changegroup hook: HG_NODE=5fed3813f7f5e1824344fdc9cf8f63bb662c292d HG_SOURCE=pull HG_URL=http://localhost:$HGPORT1/ 
   pulling from http://localhost:$HGPORT1/
   searching for changes
   adding changesets
   adding manifests
   adding file changes
   added 1 changesets with 1 changes to 1 files
+  changegroup hook: HG_NODE=5fed3813f7f5e1824344fdc9cf8f63bb662c292d HG_SOURCE=pull HG_URL=http://localhost:$HGPORT1/ 
   (run 'hg update' to get a working copy)
   $ cd ..
diff --git a/tests/test-https.t b/tests/test-https.t
--- a/tests/test-https.t
+++ b/tests/test-https.t
@@ -134,13 +134,13 @@ pull without cacert
   $ echo "changegroup = python '$TESTDIR'/printenv.py changegroup" >> .hg/hgrc
   $ hg pull
   warning: localhost certificate with fingerprint 91:4f:1a:ff:87:24:9c:09:b6:85:9b:88:b1:90:6d:30:75:64:91:ca not verified (check hostfingerprints or web.cacerts config setting)
-  changegroup hook: HG_NODE=5fed3813f7f5e1824344fdc9cf8f63bb662c292d HG_SOURCE=pull HG_URL=https://localhost:$HGPORT/ 
   pulling from https://localhost:$HGPORT/
   searching for changes
   adding changesets
   adding manifests
   adding file changes
   added 1 changesets with 1 changes to 1 files
+  changegroup hook: HG_NODE=5fed3813f7f5e1824344fdc9cf8f63bb662c292d HG_SOURCE=pull HG_URL=https://localhost:$HGPORT/ 
   warning: localhost certificate with fingerprint 91:4f:1a:ff:87:24:9c:09:b6:85:9b:88:b1:90:6d:30:75:64:91:ca not verified (check hostfingerprints or web.cacerts config setting)
   (run 'hg update' to get a working copy)
   $ cd ..
diff --git a/tests/test-merge-symlinks.t b/tests/test-merge-symlinks.t
--- a/tests/test-merge-symlinks.t
+++ b/tests/test-merge-symlinks.t
@@ -38,11 +38,11 @@ Merge them and display *_ISLINK vars
 merge heads
 
   $ hg merge --tool="python ../echo.py"
+  merging l
   HG_FILE l
   HG_MY_ISLINK 1
   HG_OTHER_ISLINK 0
   HG_BASE_ISLINK 0
-  merging l
   0 files updated, 1 files merged, 0 files removed, 0 files unresolved
   (branch merge, don't forget to commit)
 
@@ -54,9 +54,9 @@ merge working directory
   1 files updated, 0 files merged, 1 files removed, 0 files unresolved
   $ hg copy l l2
   $ HGMERGE="python ../echo.py" hg up 3
+  merging l2
   HG_FILE l2
   HG_MY_ISLINK 1
   HG_OTHER_ISLINK 0
   HG_BASE_ISLINK 0
-  merging l2
   0 files updated, 1 files merged, 0 files removed, 0 files unresolved
diff --git a/tests/test-merge-tools.t b/tests/test-merge-tools.t
--- a/tests/test-merge-tools.t
+++ b/tests/test-merge-tools.t
@@ -219,13 +219,13 @@ but true.executable set to cat found in 
   true.executable=cat
   # hg update -C 1
   # hg merge -r 2
+  merging f
   revision 1
   space
   revision 0
   space
   revision 2
   space
-  merging f
   0 files updated, 1 files merged, 0 files removed, 0 files unresolved
   (branch merge, don't forget to commit)
   # cat f
@@ -244,13 +244,13 @@ and true.executable set to cat with path
   true.executable=cat
   # hg update -C 1
   # hg merge -r 2 --config merge-tools.true.executable=cat
+  merging f
   revision 1
   space
   revision 0
   space
   revision 2
   space
-  merging f
   0 files updated, 1 files merged, 0 files removed, 0 files unresolved
   (branch merge, don't forget to commit)
   # cat f
@@ -598,6 +598,7 @@ Default is silent simplemerge:
   true.executable=cat
   # hg update -C 1
   # hg merge -r 3 --config merge-tools.true.premerge=False
+  merging f
   revision 1
   space
   revision 0
@@ -605,7 +606,6 @@ Default is silent simplemerge:
   revision 0
   space
   revision 3
-  merging f
   0 files updated, 1 files merged, 0 files removed, 0 files unresolved
   (branch merge, don't forget to commit)
   # cat f
@@ -631,6 +631,7 @@ Tool execution
   # hg update -C 1
   $ hg merge -r 2 --config merge-tools.true.executable=head --config merge-tools.true.args='$base $local $other $output' \
   >   | sed 's,==> .* <==,==> ... <==,g'
+  merging f
   ==> ... <==
   revision 0
   space
@@ -646,7 +647,6 @@ Tool execution
   ==> ... <==
   revision 1
   space
-  merging f
   0 files updated, 1 files merged, 0 files removed, 0 files unresolved
   (branch merge, don't forget to commit)
   $ aftermerge
@@ -757,13 +757,13 @@ cat is a bad merge-tool and doesn't chan
   true.executable=cat
   # hg update -C 1
   # hg merge -y -r 2 --config merge-tools.true.checkchanged=1
+  merging f
   revision 1
   space
   revision 0
   space
   revision 2
   space
-  merging f
    output file f appears unchanged
   was merge successful (yn)? n
   merging f failed!
diff --git a/tests/test-merge1.t b/tests/test-merge1.t
--- a/tests/test-merge1.t
+++ b/tests/test-merge1.t
@@ -72,8 +72,8 @@ merge should fail
   [255]
 merge of b expected
   $ hg merge -f 1
+  merging b
   merging for b
-  merging b
   0 files updated, 1 files merged, 0 files removed, 0 files unresolved
   (branch merge, don't forget to commit)
   $ hg diff --nodates
@@ -153,8 +153,8 @@ merge of b should fail
   [255]
 merge of b expected
   $ hg merge -f 2
+  merging b
   merging for b
-  merging b
   0 files updated, 1 files merged, 0 files removed, 0 files unresolved
   (branch merge, don't forget to commit)
   $ hg diff --nodates
diff --git a/tests/test-patchbomb.t b/tests/test-patchbomb.t
--- a/tests/test-patchbomb.t
+++ b/tests/test-patchbomb.t
@@ -159,12 +159,12 @@
   $ hg email -m test.mbox -f quux -t foo -c bar -s test 0:tip \
   > --config extensions.progress= --config progress.assume-tty=1 \
   > --config progress.delay=0 --config progress.refresh=0
-  \rwriting [                                                                 ] 0/3\rwriting [                                                                 ] 0/3\r                                                                                \r\r                                                                                \r\rwriting [====================>                                            ] 1/3\rwriting [====================>                                            ] 1/3\r                                                                                \r\r                                                                                \r\rwriting [==========================================>                      ] 2/3\rwriting [==========================================>                      ] 2/3\r                                                                                \rThis patch series consists of 2 patches. (esc)
+  This patch series consists of 2 patches.
   
   
   Write the introductory message for the patch series.
   
-  
+  \rwriting [                                                                 ] 0/3\rwriting [                                                                 ] 0/3\r                                                                                \r\r                                                                                \r\rwriting [====================>                                            ] 1/3\rwriting [====================>                                            ] 1/3\r                                                                                \r\r                                                                                \r\rwriting [==========================================>                      ] 2/3\rwriting [==========================================>                      ] 2/3\r                                                                                \r (esc)
   Writing [PATCH 0 of 2] test ...
   Writing [PATCH 1 of 2] a ...
   Writing [PATCH 2 of 2] b ...
diff --git a/tests/test-pull-pull-corruption.t b/tests/test-pull-pull-corruption.t
--- a/tests/test-pull-pull-corruption.t
+++ b/tests/test-pull-pull-corruption.t
@@ -42,10 +42,10 @@ start a pull...
 ... and start another pull before the first one has finished
 
   $ sleep 1
+  pulling from ../source1
+  requesting all changes
   $ hg pull ../source2 2>/dev/null
   pulling from ../source2
-  pulling from ../source1
-  requesting all changes
   adding changesets
   adding manifests
   adding file changes
diff --git a/tests/test-static-http.t b/tests/test-static-http.t
--- a/tests/test-static-http.t
+++ b/tests/test-static-http.t
@@ -68,13 +68,13 @@ check for HTTP opener failures when cach
   $ echo '[hooks]' >> .hg/hgrc
   $ echo 'changegroup = python "$TESTDIR"/printenv.py changegroup' >> .hg/hgrc
   $ hg pull
-  changegroup hook: HG_NODE=4ac2e3648604439c580c69b09ec9d93a88d93432 HG_SOURCE=pull HG_URL=http://localhost:$HGPORT/remote 
   pulling from static-http://localhost:$HGPORT/remote
   searching for changes
   adding changesets
   adding manifests
   adding file changes
   added 1 changesets with 1 changes to 1 files
+  changegroup hook: HG_NODE=4ac2e3648604439c580c69b09ec9d93a88d93432 HG_SOURCE=pull HG_URL=http://localhost:$HGPORT/remote 
   (run 'hg update' to get a working copy)
 
 trying to push