view tests/test-mq-header-from.t @ 27430:e240e914d226 stable

revlog: seek to end of file before writing (issue4943)

Revlogs were recently refactored to open file handles in "a+" and use a
persistent file handle for reading and writing. This drastically
reduced the number of file handles being opened.

Unfortunately, it appears that some versions of Solaris lose the file
offset when performing a write after the handle has been seeked.

The simplest workaround is to seek to EOF on files opened in a+ mode
before writing to them, which is what this patch does.

Ideally, this code would exist in the vfs layer. However, this would
require creating a proxy class for file objects in order to provide a
custom implementation of write(). This would add overhead. Since
revlogs are the only files we open in a+ mode, the one-off workaround
in revlog.py should be sufficient.

This patch appears to have little to no impact on performance on my
Linux machine.

  $ echo "[extensions]" >> $HGRCPATH
  $ echo "mq=" >> $HGRCPATH
  $ echo "[diff]" >> $HGRCPATH
  $ echo "nodates=true" >> $HGRCPATH
  $ catlog() {
  >     cat .hg/patches/$1.patch | sed -e "s/^diff \-r [0-9a-f]* /diff -r ... /" \
  >                                    -e "s/^\(# Parent \).*/\1/"
  >     hg log --template "{rev}: {desc} - {author}\n"
  > }
  $ runtest() {
  >     echo ==== init
  >     hg init a
  >     cd a
  >     hg qinit
  > 
  > 
  >     echo ==== qnew -U
  >     hg qnew -U 1.patch
  >     catlog 1
  > 
  >     echo ==== qref
  >     echo "1" >1
  >     hg add
  >     hg qref
  >     catlog 1
  > 
  >     echo ==== qref -u
  >     hg qref -u mary
  >     catlog 1
  > 
  >     echo ==== qnew
  >     hg qnew 2.patch
  >     echo "2" >2
  >     hg add
  >     hg qref
  >     catlog 2
  > 
  >     echo ==== qref -u
  >     hg qref -u jane
  >     catlog 2
  > 
  > 
  >     echo ==== qnew -U -m
  >     hg qnew -U -m "Three" 3.patch
  >     catlog 3
  > 
  >     echo ==== qref
  >     echo "3" >3
  >     hg add
  >     hg qref
  >     catlog 3
  > 
  >     echo ==== qref -m
  >     hg qref -m "Drei"
  >     catlog 3
  > 
  >     echo ==== qref -u
  >     hg qref -u mary
  >     catlog 3
  > 
  >     echo ==== qref -u -m
  >     hg qref -u maria -m "Three (again)"
  >     catlog 3
  > 
  >     echo ==== qnew -m
  >     hg qnew -m "Four" 4.patch
  >     echo "4" >4of t
  >     hg add
  >     hg qref
  >     catlog 4
  > 
  >     echo ==== qref -u
  >     hg qref -u jane
  >     catlog 4
  > 
  > 
  >     echo ==== qnew with HG header
  >     hg qnew --config 'mq.plain=true' 5.patch
  >     hg qpop
  >     echo "# HG changeset patch" >>.hg/patches/5.patch
  >     echo "# User johndoe" >>.hg/patches/5.patch
  >     hg qpush 2>&1 | grep 'now at'
  >     catlog 5
  > 
  >     echo ==== hg qref
  >     echo "5" >5
  >     hg add
  >     hg qref
  >     catlog 5
  > 
  >     echo ==== hg qref -U
  >     hg qref -U
  >     catlog 5
  > 
  >     echo ==== hg qref -u
  >     hg qref -u johndeere
  >     catlog 5
  > 
  > 
  >     echo ==== qnew with plain header
  >     hg qnew --config 'mq.plain=true' -U 6.patch
  >     hg qpop
  >     hg qpush 2>&1 | grep 'now at'
  >     catlog 6
  > 
  >     echo ==== hg qref
  >     echo "6" >6
  >     hg add
  >     hg qref
  >     catlog 6
  > 
  >     echo ==== hg qref -U
  >     hg qref -U
  >     catlog 6
  > 
  >     echo ==== hg qref -u
  >     hg qref -u johndeere
  >     catlog 6
  > 
  > 
  >     echo ==== "qpop -a / qpush -a"
  >     hg qpop -a
  >     hg qpush -a
  >     hg log --template "{rev}: {desc} - {author}\n"
  > }

======= plain headers

  $ echo "[mq]" >> $HGRCPATH
  $ echo "plain=true" >> $HGRCPATH
  $ mkdir sandbox
  $ (cd sandbox ; runtest)
  ==== init
  ==== qnew -U
  From: test
  
  0: [mq]: 1.patch - test
  ==== qref
  adding 1
  From: test
  
  diff -r ... 1
  --- /dev/null
  +++ b/1
  @@ -0,0 +1,1 @@
  +1
  0: [mq]: 1.patch - test
  ==== qref -u
  From: mary
  
  diff -r ... 1
  --- /dev/null
  +++ b/1
  @@ -0,0 +1,1 @@
  +1
  0: [mq]: 1.patch - mary
  ==== qnew
  adding 2
  diff -r ... 2
  --- /dev/null
  +++ b/2
  @@ -0,0 +1,1 @@
  +2
  1: [mq]: 2.patch - test
  0: [mq]: 1.patch - mary
  ==== qref -u
  From: jane
  
  diff -r ... 2
  --- /dev/null
  +++ b/2
  @@ -0,0 +1,1 @@
  +2
  1: [mq]: 2.patch - jane
  0: [mq]: 1.patch - mary
  ==== qnew -U -m
  From: test
  
  Three
  
  2: Three - test
  1: [mq]: 2.patch - jane
  0: [mq]: 1.patch - mary
  ==== qref
  adding 3
  From: test
  
  Three
  
  diff -r ... 3
  --- /dev/null
  +++ b/3
  @@ -0,0 +1,1 @@
  +3
  2: Three - test
  1: [mq]: 2.patch - jane
  0: [mq]: 1.patch - mary
  ==== qref -m
  From: test
  
  Drei
  
  diff -r ... 3
  --- /dev/null
  +++ b/3
  @@ -0,0 +1,1 @@
  +3
  2: Drei - test
  1: [mq]: 2.patch - jane
  0: [mq]: 1.patch - mary
  ==== qref -u
  From: mary
  
  Drei
  
  diff -r ... 3
  --- /dev/null
  +++ b/3
  @@ -0,0 +1,1 @@
  +3
  2: Drei - mary
  1: [mq]: 2.patch - jane
  0: [mq]: 1.patch - mary
  ==== qref -u -m
  From: maria
  
  Three (again)
  
  diff -r ... 3
  --- /dev/null
  +++ b/3
  @@ -0,0 +1,1 @@
  +3
  2: Three (again) - maria
  1: [mq]: 2.patch - jane
  0: [mq]: 1.patch - mary
  ==== qnew -m
  adding 4of
  Four
  
  diff -r ... 4of
  --- /dev/null
  +++ b/4of
  @@ -0,0 +1,1 @@
  +4 t
  3: Four - test
  2: Three (again) - maria
  1: [mq]: 2.patch - jane
  0: [mq]: 1.patch - mary
  ==== qref -u
  From: jane
  
  Four
  
  diff -r ... 4of
  --- /dev/null
  +++ b/4of
  @@ -0,0 +1,1 @@
  +4 t
  3: Four - jane
  2: Three (again) - maria
  1: [mq]: 2.patch - jane
  0: [mq]: 1.patch - mary
  ==== qnew with HG header
  popping 5.patch
  now at: 4.patch
  now at: 5.patch
  # HG changeset patch
  # User johndoe
  4: imported patch 5.patch - johndoe
  3: Four - jane
  2: Three (again) - maria
  1: [mq]: 2.patch - jane
  0: [mq]: 1.patch - mary
  ==== hg qref
  adding 5
  # HG changeset patch
  # User johndoe
  # Parent 
  
  diff -r ... 5
  --- /dev/null
  +++ b/5
  @@ -0,0 +1,1 @@
  +5
  4: [mq]: 5.patch - johndoe
  3: Four - jane
  2: Three (again) - maria
  1: [mq]: 2.patch - jane
  0: [mq]: 1.patch - mary
  ==== hg qref -U
  # HG changeset patch
  # User test
  # Parent 
  
  diff -r ... 5
  --- /dev/null
  +++ b/5
  @@ -0,0 +1,1 @@
  +5
  4: [mq]: 5.patch - test
  3: Four - jane
  2: Three (again) - maria
  1: [mq]: 2.patch - jane
  0: [mq]: 1.patch - mary
  ==== hg qref -u
  # HG changeset patch
  # User johndeere
  # Parent 
  
  diff -r ... 5
  --- /dev/null
  +++ b/5
  @@ -0,0 +1,1 @@
  +5
  4: [mq]: 5.patch - johndeere
  3: Four - jane
  2: Three (again) - maria
  1: [mq]: 2.patch - jane
  0: [mq]: 1.patch - mary
  ==== qnew with plain header
  popping 6.patch
  now at: 5.patch
  now at: 6.patch
  From: test
  
  5: imported patch 6.patch - test
  4: [mq]: 5.patch - johndeere
  3: Four - jane
  2: Three (again) - maria
  1: [mq]: 2.patch - jane
  0: [mq]: 1.patch - mary
  ==== hg qref
  adding 6
  From: test
  
  diff -r ... 6
  --- /dev/null
  +++ b/6
  @@ -0,0 +1,1 @@
  +6
  5: [mq]: 6.patch - test
  4: [mq]: 5.patch - johndeere
  3: Four - jane
  2: Three (again) - maria
  1: [mq]: 2.patch - jane
  0: [mq]: 1.patch - mary
  ==== hg qref -U
  From: test
  
  diff -r ... 6
  --- /dev/null
  +++ b/6
  @@ -0,0 +1,1 @@
  +6
  5: [mq]: 6.patch - test
  4: [mq]: 5.patch - johndeere
  3: Four - jane
  2: Three (again) - maria
  1: [mq]: 2.patch - jane
  0: [mq]: 1.patch - mary
  ==== hg qref -u
  From: johndeere
  
  diff -r ... 6
  --- /dev/null
  +++ b/6
  @@ -0,0 +1,1 @@
  +6
  5: [mq]: 6.patch - johndeere
  4: [mq]: 5.patch - johndeere
  3: Four - jane
  2: Three (again) - maria
  1: [mq]: 2.patch - jane
  0: [mq]: 1.patch - mary
  ==== qpop -a / qpush -a
  popping 6.patch
  popping 5.patch
  popping 4.patch
  popping 3.patch
  popping 2.patch
  popping 1.patch
  patch queue now empty
  applying 1.patch
  applying 2.patch
  applying 3.patch
  applying 4.patch
  applying 5.patch
  applying 6.patch
  now at: 6.patch
  5: imported patch 6.patch - johndeere
  4: imported patch 5.patch - johndeere
  3: Four - jane
  2: Three (again) - maria
  1: imported patch 2.patch - jane
  0: imported patch 1.patch - mary
  $ rm -r sandbox

======= hg headers

  $ echo "plain=false" >> $HGRCPATH
  $ mkdir sandbox
  $ (cd sandbox ; runtest)
  ==== init
  ==== qnew -U
  # HG changeset patch
  # User test
  # Parent 
  
  0: [mq]: 1.patch - test
  ==== qref
  adding 1
  # HG changeset patch
  # User test
  # Parent 
  
  diff -r ... 1
  --- /dev/null
  +++ b/1
  @@ -0,0 +1,1 @@
  +1
  0: [mq]: 1.patch - test
  ==== qref -u
  # HG changeset patch
  # User mary
  # Parent 
  
  diff -r ... 1
  --- /dev/null
  +++ b/1
  @@ -0,0 +1,1 @@
  +1
  0: [mq]: 1.patch - mary
  ==== qnew
  adding 2
  # HG changeset patch
  # Parent 
  
  diff -r ... 2
  --- /dev/null
  +++ b/2
  @@ -0,0 +1,1 @@
  +2
  1: [mq]: 2.patch - test
  0: [mq]: 1.patch - mary
  ==== qref -u
  # HG changeset patch
  # User jane
  # Parent 
  
  diff -r ... 2
  --- /dev/null
  +++ b/2
  @@ -0,0 +1,1 @@
  +2
  1: [mq]: 2.patch - jane
  0: [mq]: 1.patch - mary
  ==== qnew -U -m
  # HG changeset patch
  # User test
  # Parent 
  Three
  
  2: Three - test
  1: [mq]: 2.patch - jane
  0: [mq]: 1.patch - mary
  ==== qref
  adding 3
  # HG changeset patch
  # User test
  # Parent 
  Three
  
  diff -r ... 3
  --- /dev/null
  +++ b/3
  @@ -0,0 +1,1 @@
  +3
  2: Three - test
  1: [mq]: 2.patch - jane
  0: [mq]: 1.patch - mary
  ==== qref -m
  # HG changeset patch
  # User test
  # Parent 
  Drei
  
  diff -r ... 3
  --- /dev/null
  +++ b/3
  @@ -0,0 +1,1 @@
  +3
  2: Drei - test
  1: [mq]: 2.patch - jane
  0: [mq]: 1.patch - mary
  ==== qref -u
  # HG changeset patch
  # User mary
  # Parent 
  Drei
  
  diff -r ... 3
  --- /dev/null
  +++ b/3
  @@ -0,0 +1,1 @@
  +3
  2: Drei - mary
  1: [mq]: 2.patch - jane
  0: [mq]: 1.patch - mary
  ==== qref -u -m
  # HG changeset patch
  # User maria
  # Parent 
  Three (again)
  
  diff -r ... 3
  --- /dev/null
  +++ b/3
  @@ -0,0 +1,1 @@
  +3
  2: Three (again) - maria
  1: [mq]: 2.patch - jane
  0: [mq]: 1.patch - mary
  ==== qnew -m
  adding 4of
  # HG changeset patch
  # Parent 
  Four
  
  diff -r ... 4of
  --- /dev/null
  +++ b/4of
  @@ -0,0 +1,1 @@
  +4 t
  3: Four - test
  2: Three (again) - maria
  1: [mq]: 2.patch - jane
  0: [mq]: 1.patch - mary
  ==== qref -u
  # HG changeset patch
  # User jane
  # Parent 
  Four
  
  diff -r ... 4of
  --- /dev/null
  +++ b/4of
  @@ -0,0 +1,1 @@
  +4 t
  3: Four - jane
  2: Three (again) - maria
  1: [mq]: 2.patch - jane
  0: [mq]: 1.patch - mary
  ==== qnew with HG header
  popping 5.patch
  now at: 4.patch
  now at: 5.patch
  # HG changeset patch
  # User johndoe
  4: imported patch 5.patch - johndoe
  3: Four - jane
  2: Three (again) - maria
  1: [mq]: 2.patch - jane
  0: [mq]: 1.patch - mary
  ==== hg qref
  adding 5
  # HG changeset patch
  # User johndoe
  # Parent 
  
  diff -r ... 5
  --- /dev/null
  +++ b/5
  @@ -0,0 +1,1 @@
  +5
  4: [mq]: 5.patch - johndoe
  3: Four - jane
  2: Three (again) - maria
  1: [mq]: 2.patch - jane
  0: [mq]: 1.patch - mary
  ==== hg qref -U
  # HG changeset patch
  # User test
  # Parent 
  
  diff -r ... 5
  --- /dev/null
  +++ b/5
  @@ -0,0 +1,1 @@
  +5
  4: [mq]: 5.patch - test
  3: Four - jane
  2: Three (again) - maria
  1: [mq]: 2.patch - jane
  0: [mq]: 1.patch - mary
  ==== hg qref -u
  # HG changeset patch
  # User johndeere
  # Parent 
  
  diff -r ... 5
  --- /dev/null
  +++ b/5
  @@ -0,0 +1,1 @@
  +5
  4: [mq]: 5.patch - johndeere
  3: Four - jane
  2: Three (again) - maria
  1: [mq]: 2.patch - jane
  0: [mq]: 1.patch - mary
  ==== qnew with plain header
  popping 6.patch
  now at: 5.patch
  now at: 6.patch
  From: test
  
  5: imported patch 6.patch - test
  4: [mq]: 5.patch - johndeere
  3: Four - jane
  2: Three (again) - maria
  1: [mq]: 2.patch - jane
  0: [mq]: 1.patch - mary
  ==== hg qref
  adding 6
  From: test
  
  diff -r ... 6
  --- /dev/null
  +++ b/6
  @@ -0,0 +1,1 @@
  +6
  5: [mq]: 6.patch - test
  4: [mq]: 5.patch - johndeere
  3: Four - jane
  2: Three (again) - maria
  1: [mq]: 2.patch - jane
  0: [mq]: 1.patch - mary
  ==== hg qref -U
  From: test
  
  diff -r ... 6
  --- /dev/null
  +++ b/6
  @@ -0,0 +1,1 @@
  +6
  5: [mq]: 6.patch - test
  4: [mq]: 5.patch - johndeere
  3: Four - jane
  2: Three (again) - maria
  1: [mq]: 2.patch - jane
  0: [mq]: 1.patch - mary
  ==== hg qref -u
  From: johndeere
  
  diff -r ... 6
  --- /dev/null
  +++ b/6
  @@ -0,0 +1,1 @@
  +6
  5: [mq]: 6.patch - johndeere
  4: [mq]: 5.patch - johndeere
  3: Four - jane
  2: Three (again) - maria
  1: [mq]: 2.patch - jane
  0: [mq]: 1.patch - mary
  ==== qpop -a / qpush -a
  popping 6.patch
  popping 5.patch
  popping 4.patch
  popping 3.patch
  popping 2.patch
  popping 1.patch
  patch queue now empty
  applying 1.patch
  applying 2.patch
  applying 3.patch
  applying 4.patch
  applying 5.patch
  applying 6.patch
  now at: 6.patch
  5: imported patch 6.patch - johndeere
  4: imported patch 5.patch - johndeere
  3: Four - jane
  2: Three (again) - maria
  1: imported patch 2.patch - jane
  0: imported patch 1.patch - mary
  $ rm -r sandbox
  $ runtest
  ==== init
  ==== qnew -U
  # HG changeset patch
  # User test
  # Parent 
  
  0: [mq]: 1.patch - test
  ==== qref
  adding 1
  # HG changeset patch
  # User test
  # Parent 
  
  diff -r ... 1
  --- /dev/null
  +++ b/1
  @@ -0,0 +1,1 @@
  +1
  0: [mq]: 1.patch - test
  ==== qref -u
  # HG changeset patch
  # User mary
  # Parent 
  
  diff -r ... 1
  --- /dev/null
  +++ b/1
  @@ -0,0 +1,1 @@
  +1
  0: [mq]: 1.patch - mary
  ==== qnew
  adding 2
  # HG changeset patch
  # Parent 
  
  diff -r ... 2
  --- /dev/null
  +++ b/2
  @@ -0,0 +1,1 @@
  +2
  1: [mq]: 2.patch - test
  0: [mq]: 1.patch - mary
  ==== qref -u
  # HG changeset patch
  # User jane
  # Parent 
  
  diff -r ... 2
  --- /dev/null
  +++ b/2
  @@ -0,0 +1,1 @@
  +2
  1: [mq]: 2.patch - jane
  0: [mq]: 1.patch - mary
  ==== qnew -U -m
  # HG changeset patch
  # User test
  # Parent 
  Three
  
  2: Three - test
  1: [mq]: 2.patch - jane
  0: [mq]: 1.patch - mary
  ==== qref
  adding 3
  # HG changeset patch
  # User test
  # Parent 
  Three
  
  diff -r ... 3
  --- /dev/null
  +++ b/3
  @@ -0,0 +1,1 @@
  +3
  2: Three - test
  1: [mq]: 2.patch - jane
  0: [mq]: 1.patch - mary
  ==== qref -m
  # HG changeset patch
  # User test
  # Parent 
  Drei
  
  diff -r ... 3
  --- /dev/null
  +++ b/3
  @@ -0,0 +1,1 @@
  +3
  2: Drei - test
  1: [mq]: 2.patch - jane
  0: [mq]: 1.patch - mary
  ==== qref -u
  # HG changeset patch
  # User mary
  # Parent 
  Drei
  
  diff -r ... 3
  --- /dev/null
  +++ b/3
  @@ -0,0 +1,1 @@
  +3
  2: Drei - mary
  1: [mq]: 2.patch - jane
  0: [mq]: 1.patch - mary
  ==== qref -u -m
  # HG changeset patch
  # User maria
  # Parent 
  Three (again)
  
  diff -r ... 3
  --- /dev/null
  +++ b/3
  @@ -0,0 +1,1 @@
  +3
  2: Three (again) - maria
  1: [mq]: 2.patch - jane
  0: [mq]: 1.patch - mary
  ==== qnew -m
  adding 4of
  # HG changeset patch
  # Parent 
  Four
  
  diff -r ... 4of
  --- /dev/null
  +++ b/4of
  @@ -0,0 +1,1 @@
  +4 t
  3: Four - test
  2: Three (again) - maria
  1: [mq]: 2.patch - jane
  0: [mq]: 1.patch - mary
  ==== qref -u
  # HG changeset patch
  # User jane
  # Parent 
  Four
  
  diff -r ... 4of
  --- /dev/null
  +++ b/4of
  @@ -0,0 +1,1 @@
  +4 t
  3: Four - jane
  2: Three (again) - maria
  1: [mq]: 2.patch - jane
  0: [mq]: 1.patch - mary
  ==== qnew with HG header
  popping 5.patch
  now at: 4.patch
  now at: 5.patch
  # HG changeset patch
  # User johndoe
  4: imported patch 5.patch - johndoe
  3: Four - jane
  2: Three (again) - maria
  1: [mq]: 2.patch - jane
  0: [mq]: 1.patch - mary
  ==== hg qref
  adding 5
  # HG changeset patch
  # User johndoe
  # Parent 
  
  diff -r ... 5
  --- /dev/null
  +++ b/5
  @@ -0,0 +1,1 @@
  +5
  4: [mq]: 5.patch - johndoe
  3: Four - jane
  2: Three (again) - maria
  1: [mq]: 2.patch - jane
  0: [mq]: 1.patch - mary
  ==== hg qref -U
  # HG changeset patch
  # User test
  # Parent 
  
  diff -r ... 5
  --- /dev/null
  +++ b/5
  @@ -0,0 +1,1 @@
  +5
  4: [mq]: 5.patch - test
  3: Four - jane
  2: Three (again) - maria
  1: [mq]: 2.patch - jane
  0: [mq]: 1.patch - mary
  ==== hg qref -u
  # HG changeset patch
  # User johndeere
  # Parent 
  
  diff -r ... 5
  --- /dev/null
  +++ b/5
  @@ -0,0 +1,1 @@
  +5
  4: [mq]: 5.patch - johndeere
  3: Four - jane
  2: Three (again) - maria
  1: [mq]: 2.patch - jane
  0: [mq]: 1.patch - mary
  ==== qnew with plain header
  popping 6.patch
  now at: 5.patch
  now at: 6.patch
  From: test
  
  5: imported patch 6.patch - test
  4: [mq]: 5.patch - johndeere
  3: Four - jane
  2: Three (again) - maria
  1: [mq]: 2.patch - jane
  0: [mq]: 1.patch - mary
  ==== hg qref
  adding 6
  From: test
  
  diff -r ... 6
  --- /dev/null
  +++ b/6
  @@ -0,0 +1,1 @@
  +6
  5: [mq]: 6.patch - test
  4: [mq]: 5.patch - johndeere
  3: Four - jane
  2: Three (again) - maria
  1: [mq]: 2.patch - jane
  0: [mq]: 1.patch - mary
  ==== hg qref -U
  From: test
  
  diff -r ... 6
  --- /dev/null
  +++ b/6
  @@ -0,0 +1,1 @@
  +6
  5: [mq]: 6.patch - test
  4: [mq]: 5.patch - johndeere
  3: Four - jane
  2: Three (again) - maria
  1: [mq]: 2.patch - jane
  0: [mq]: 1.patch - mary
  ==== hg qref -u
  From: johndeere
  
  diff -r ... 6
  --- /dev/null
  +++ b/6
  @@ -0,0 +1,1 @@
  +6
  5: [mq]: 6.patch - johndeere
  4: [mq]: 5.patch - johndeere
  3: Four - jane
  2: Three (again) - maria
  1: [mq]: 2.patch - jane
  0: [mq]: 1.patch - mary
  ==== qpop -a / qpush -a
  popping 6.patch
  popping 5.patch
  popping 4.patch
  popping 3.patch
  popping 2.patch
  popping 1.patch
  patch queue now empty
  applying 1.patch
  applying 2.patch
  applying 3.patch
  applying 4.patch
  applying 5.patch
  applying 6.patch
  now at: 6.patch
  5: imported patch 6.patch - johndeere
  4: imported patch 5.patch - johndeere
  3: Four - jane
  2: Three (again) - maria
  1: imported patch 2.patch - jane
  0: imported patch 1.patch - mary

  $ cd ..