apply: refactor `struct image` to use a `struct strbuf`

The `struct image` uses a character array to track the pre- or postimage
of a patch operation. This has multiple downsides:

  - It is somewhat hard to track memory ownership. In fact, we have
    several memory leaks in git-apply(1) because we do not (and cannot
    easily) free the buffer in all situations.

  - We have to reinvent the wheel and manually implement a lot of
    functionality that would already be provided by `struct strbuf`.

  - We have to carefully track whether `update_pre_post_images()` can do
    an in-place update of the postimage or whether it has to allocate a
    new buffer for it.

This is all rather cumbersome, and especially `update_pre_post_images()`
is really hard to understand as a consequence even though what it is
doing is rather trivial.

Refactor the code to use a `struct strbuf` instead, addressing all of
the above. Like this we can easily perform in-place updates in all
situations, the logic to perform those updates becomes way simpler and
the lifetime of the buffer becomes a ton easier to track.

This refactoring also plugs some leaking buffers as a side effect.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

5 files changed, 6 insertions, 2 deletions

diff --git a/t/t3436-rebase-more-options.sh b/t/t3436-rebase-more-options.sh
index 94671d3c46..4d9744e5fc 100755
--- a/t/t3436-rebase-more-options.sh
+++ b/t/t3436-rebase-more-options.sh
@@ -5,6 +5,7 @@
 
 test_description='tests to ensure compatibility between am and interactive backends'
 
+TEST_PASSES_SANITIZE_LEAK=true
 . ./test-lib.sh
 
 . "$TEST_DIRECTORY"/lib-rebase.sh
diff --git a/t/t4107-apply-ignore-whitespace.sh b/t/t4107-apply-ignore-whitespace.sh
index ac72eeaf27..5e6e203aa5 100755
--- a/t/t4107-apply-ignore-whitespace.sh
+++ b/t/t4107-apply-ignore-whitespace.sh
@@ -3,9 +3,9 @@
 # Copyright (c) 2009 Giuseppe Bilotta
 #
 
-test_description='git-apply --ignore-whitespace.
+test_description='git-apply --ignore-whitespace.'
 
-'
+TEST_PASSES_SANITIZE_LEAK=true
 . ./test-lib.sh
 
 # This primes main.c file that indents without using HT at all.
diff --git a/t/t4124-apply-ws-rule.sh b/t/t4124-apply-ws-rule.sh
index 485c7d2d12..cdffee0273 100755
--- a/t/t4124-apply-ws-rule.sh
+++ b/t/t4124-apply-ws-rule.sh
@@ -2,6 +2,7 @@
 
 test_description='core.whitespace rules and git apply'
 
+TEST_PASSES_SANITIZE_LEAK=true
 . ./test-lib.sh
 
 prepare_test_file () {
diff --git a/t/t4125-apply-ws-fuzz.sh b/t/t4125-apply-ws-fuzz.sh
index 090987c89b..f248cc2a00 100755
--- a/t/t4125-apply-ws-fuzz.sh
+++ b/t/t4125-apply-ws-fuzz.sh
@@ -2,6 +2,7 @@
 
 test_description='applying patch that has broken whitespaces in context'
 
+TEST_PASSES_SANITIZE_LEAK=true
 . ./test-lib.sh
 
 test_expect_success setup '
diff --git a/t/t4138-apply-ws-expansion.sh b/t/t4138-apply-ws-expansion.sh
index 8bbf8260fa..7981931b4e 100755
--- a/t/t4138-apply-ws-expansion.sh
+++ b/t/t4138-apply-ws-expansion.sh
@@ -5,6 +5,7 @@
 
 test_description='git apply test patches with whitespace expansion.'
 
+TEST_PASSES_SANITIZE_LEAK=true
 . ./test-lib.sh
 
 test_expect_success setup '