commit: discard partial cache before (re-)reading it

The read_cache() in prepare_to_commit() would end up clobbering the
pointer we had for a previously populated "the_index.cache_tree" in
the very common case of "git commit" stressed by e.g. the tests being
changed here.

We'd populate "the_index.cache_tree" by calling
"update_main_cache_tree" in prepare_index(), but would not end up with
a "fully prepared" index. What constitutes an existing index is
clearly overly fuzzy, here we'll check "active_nr" (aka
"the_index.cache_nr"), but our "the_index.cache_tree" might have been
malloc()'d already.

Thus the code added in 11c8a74a64 (commit: write cache-tree data when
writing index anyway, 2011-12-06) would end up allocating the
"cache_tree", and would interact here with code added in
7168624c35 (Do not generate full commit log message if it is not
going to be used, 2007-11-28). The result was a very common memory
leak.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Taylor Blau <me@ttaylorr.com>

builtin/commit.c

@@ -987,8 +987,11 @@ static int prepare_to_commit(const char *index_file, const char *prefix,
 		struct object_id oid;
 		const char *parent = "HEAD";
 
-		if (!active_nr && read_cache() < 0)
-			die(_("Cannot read index"));
+		if (!active_nr) {
+			discard_cache();
+			if (read_cache() < 0)
+				die(_("Cannot read index"));
+		}
 
 		if (amend)
 			parent = "HEAD^1";

t/t0068-for-each-repo.sh

@@ -2,6 +2,7 @@
 
 test_description='git for-each-repo builtin'
 
+TEST_PASSES_SANITIZE_LEAK=true
 . ./test-lib.sh
 
 test_expect_success 'run based on configured value' '

t/t0070-fundamental.sh

@@ -6,6 +6,7 @@ test_description='check that the most basic functions work
 Verify wrappers and compatibility functions.
 '
 
+TEST_PASSES_SANITIZE_LEAK=true
 . ./test-lib.sh
 
 test_expect_success 'character classes (isspace, isalpha etc.)' '

t/t1404-update-ref-errors.sh

@@ -1,6 +1,8 @@
 #!/bin/sh
 
 test_description='Test git update-ref error handling'
+
+TEST_PASSES_SANITIZE_LEAK=true
 . ./test-lib.sh
 
 # Create some references, perhaps run pack-refs --all, then try to

t/t1409-avoid-packing-refs.sh

@@ -2,6 +2,7 @@
 
 test_description='avoid rewriting packed-refs unnecessarily'
 
+TEST_PASSES_SANITIZE_LEAK=true
 . ./test-lib.sh
 
 # Add an identifying mark to the packed-refs file header line. This

t/t1413-reflog-detach.sh

@@ -4,6 +4,7 @@ test_description='Test reflog interaction with detached HEAD'
 GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME=main
 export GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME
 
+TEST_PASSES_SANITIZE_LEAK=true
 . ./test-lib.sh
 
 reset_state () {

t/t1501-work-tree.sh

@@ -1,6 +1,8 @@
 #!/bin/sh
 
 test_description='test separate work tree'
+
+TEST_PASSES_SANITIZE_LEAK=true
 . ./test-lib.sh
 
 test_expect_success 'setup' '

t/t2025-checkout-no-overlay.sh

@@ -2,6 +2,7 @@
 
 test_description='checkout --no-overlay <tree-ish> -- <pathspec>'
 
+TEST_PASSES_SANITIZE_LEAK=true
 . ./test-lib.sh
 
 test_expect_success 'setup' '

t/t3009-ls-files-others-nonsubmodule.sh

@@ -18,6 +18,7 @@ This test runs git ls-files --others with the following working tree:
       git repository with a commit and an untracked file
 '
 
+TEST_PASSES_SANITIZE_LEAK=true
 . ./test-lib.sh
 
 test_expect_success 'setup: directories' '

t/t3010-ls-files-killed-modified.sh

@@ -41,6 +41,8 @@ Also for modification test, the cache and working tree have:
 We should report path0, path1, path2/file2, path3/file3, path7 and path8
 modified without reporting path9 and path10.  submod1 is also modified.
 '
+
+TEST_PASSES_SANITIZE_LEAK=true
 . ./test-lib.sh
 
 test_expect_success 'git update-index --add to add various paths.' '

t/t4045-diff-relative.sh

@@ -1,6 +1,8 @@
 #!/bin/sh
 
 test_description='diff --relative tests'
+
+TEST_PASSES_SANITIZE_LEAK=true
 . ./test-lib.sh
 
 test_expect_success 'setup' '

t/t4111-apply-subdir.sh

@@ -2,6 +2,7 @@
 
 test_description='patching from inconvenient places'
 
+TEST_PASSES_SANITIZE_LEAK=true
 . ./test-lib.sh
 
 test_expect_success 'setup' '

t/t4135-apply-weird-filenames.sh

@@ -2,6 +2,7 @@
 
 test_description='git apply with weird postimage filenames'
 
+TEST_PASSES_SANITIZE_LEAK=true
 . ./test-lib.sh
 
 test_expect_success 'setup' '

t/t4213-log-tabexpand.sh

@@ -2,6 +2,7 @@
 
 test_description='log/show --expand-tabs'
 
+TEST_PASSES_SANITIZE_LEAK=true
 . ./test-lib.sh
 
 HT="	"

t/t5618-alternate-refs.sh

@@ -1,6 +1,8 @@
 #!/bin/sh
 
 test_description='test handling of --alternate-refs traversal'
+
+TEST_PASSES_SANITIZE_LEAK=true
 . ./test-lib.sh
 
 # Avoid test_commit because we want a specific and known set of refs:

t/t6301-for-each-ref-errors.sh

@@ -2,6 +2,7 @@
 
 test_description='for-each-ref errors for broken refs'
 
+TEST_PASSES_SANITIZE_LEAK=true
 . ./test-lib.sh
 
 ZEROS=$ZERO_OID

t/t7520-ignored-hook-warning.sh

@@ -2,6 +2,7 @@
 
 test_description='ignored hook warning'
 
+TEST_PASSES_SANITIZE_LEAK=true
 . ./test-lib.sh
 
 test_expect_success setup '

t/t7614-merge-signoff.sh

@@ -8,6 +8,7 @@ This test runs git merge --signoff and makes sure that it works.
 GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME=main
 export GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME
 
+TEST_PASSES_SANITIZE_LEAK=true
 . ./test-lib.sh
 
 # Setup test files

t/t9003-help-autocorrect.sh

@@ -1,6 +1,8 @@
 #!/bin/sh
 
 test_description='help.autocorrect finding a match'
+
+TEST_PASSES_SANITIZE_LEAK=true
 . ./test-lib.sh
 
 test_expect_success 'setup' '