[PATCH 6/9] Fix a seriously bad interaction between .git caching and repo cloning

[Yann Dirson <ydirson@altern.org>]

Testcase 2 exhibits a problem with caching the location of .git while
cloning a repository.  Since basedir.get() is called before the clone is
built, a value may get stored in the cache if we are within a
git-controlled tree already.  Then when constructing the object for the
clone, a bogus .git is used, which can lead, when running tests in t/trash,
to corruption of the stgit .git repository.

Testcase 1 does not show any problem by chance, because since we have a
./.git prepared for use by the testsuite, value ".git" get cached, and it
happens that this value will be still valid after chdir'ing into the
newborn clone.

Clearing the cache at the appropriate place fixes the problem.

Signed-off-by: Yann Dirson <ydirson@altern.org>
---

 stgit/basedir.py        |    6 ++++++
 stgit/commands/clone.py |    3 +++
 t/t1100-clone-under.sh  |   36 ++++++++++++++++++++++++++++++++++++
 3 files changed, 45 insertions(+), 0 deletions(-)

diff --git a/stgit/basedir.py b/stgit/basedir.py
index c394572..81f2b40 100644
--- a/stgit/basedir.py
+++ b/stgit/basedir.py
@@ -42,3 +42,9 @@ def get():
             __base_dir = __output('git-rev-parse --git-dir 2> /dev/null')
 
     return __base_dir
+
+def clear_cache():
+    """Clear the cached location of .git
+    """
+    global __base_dir
+    __base_dir = None
diff --git a/stgit/commands/clone.py b/stgit/commands/clone.py
index 9ad76a6..455dd6e 100644
--- a/stgit/commands/clone.py
+++ b/stgit/commands/clone.py
@@ -51,6 +51,9 @@ def func(parser, options, args):
     os.chdir(local_dir)
     git.checkout(tree_id = 'HEAD')
 
+    # be sure to forget any cached value for .git, since we're going
+    # to work on a brand new repository
+    basedir.clear_cache()
     stack.Series().init()
 
     print 'done'
diff --git a/t/t1100-clone-under.sh b/t/t1100-clone-under.sh
new file mode 100755
index 0000000..c86ef61
--- /dev/null
+++ b/t/t1100-clone-under.sh
@@ -0,0 +1,36 @@
+#!/bin/sh
+#
+# Copyright (c) 2006 Yann Dirson
+#
+
+test_description='Check cloning in a repo subdir
+
+Check that "stg clone" works in a subdir of a git tree.
+This ensures (to some point) that a clone within a tree does
+not corrupt the enclosing repo.
+
+This test must be run before any tests making use of clone.
+'
+
+. ./test-lib.sh
+
+# Here we are in a repo, we have a ./.git
+# Do not get rid of it, or a bug may bite out stgit repo hard
+
+# Need a repo to clone
+test_create_repo foo
+
+test_expect_success \
+    'stg clone right inside a git tree' \
+    "stg clone foo bar"
+
+# now work in a subdir
+mkdir sub
+mv foo sub
+cd sub
+
+test_expect_success \
+    'stg clone deeper under a git tree' \
+    "stg clone foo bar"
+
+test_done