[PATCH] submodule--helper: normalize funny urls

Stefan Beller· Oct 18, 2016, 17:52 UTC · lore

The remote URL for the submodule can be specified relative to the URL of the superproject in .gitmodules. A top-level git://site.xz/toplevel.git can specify in its .gitmodules

        [submodule "sub"]
                url = ../submodule.git
                path = sub

to say that git://site.xz/submodule.git is where the submodule bound at its "sub/" is found.

However, when the toplevel is cloned like this:

        git clone git://site.xz/toplevel.git/. top

i.e. the toplevel specifies its URL with trailing "/.", the code set the URL to git://site.xz/toplevel.git/submodule.git for the submodule, which is nonsense. This was because the logic failed to treat trailing "/." any differently from trailing "/<anything-without-slash>" when resolving a relative URL "../<something>" off of it. Stripping "/." at the end does *not* take you one level up, even though stripping "/<anything-without-slash>" does!

Some users may rely on this by always cloning with '/.' and having an additional '../' in the relative path for the submodule, and this patch breaks them. So why introduce this patch?

The fix in c12922024 (submodule: ignore trailing slash on superproject URL, 2016-10-10) and prior discussion revealed, that Git and Git for Windows treat URLs differently, as currently Git for Windows strips off a trailing dot from paths when calling a Git binary unlike when running a shell. Which means Git for Windows is already doing the right thing for the case mentioned above, but it would fail our current tests, that test for the broken behavior and it would confuse users working across platforms. So we'd rather fix it in Git to ignore any of these trailing no ops in the path properly.

We never produce the URLs with a trailing '/.' in Git ourselves, they come to us, because the user used it as the URL for cloning a superproject. Normalize these paths.

Helped-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Stefan Beller <sbeller@google.com>
---

 * reworded the commit message, taken from Junio, but added more explanation
   why we want to introduce this patch. 
 * added the length check
 * use an infinite loop with break instead of a variable
   to determine the ending condition.

 builtin/submodule--helper.c | 48 +++++++++++++++++++++++++++++++++------------
 t/t0060-path-utils.sh       | 11 +++++++----
 2 files changed, 43 insertions(+), 16 deletions(-)

Show changes to 2 files +43 −16

builtin/submodule--helper.c, t/t0060-path-utils.sh

diff --git a/builtin/submodule--helper.c b/builtin/submodule--helper.c
index 260f46f..ac03cb3 100644
--- a/builtin/submodule--helper.c
+++ b/builtin/submodule--helper.c
@@ -76,6 +76,29 @@ static int chop_last_dir(char **remoteurl, int is_relative)
 	return 0;
 }
 
+static void strip_url_ending(char *url, size_t *_len)
+{
+	size_t len = _len ? *_len : strlen(url);
+
+	for (;;) {
+		if (len > 1 && is_dir_sep(url[len-2]) && url[len-1] == '.') {
+			url[len-2] = '\0';
+			len -= 2;
+			continue;
+		}
+		if (len > 0 && is_dir_sep(url[len-1])) {
+			url[len-1] = '\0';
+			len --;
+			continue;
+		}
+
+		break;
+	}
+
+	if (_len)
+		*_len = len;
+}
+
 /*
  * The `url` argument is the URL that navigates to the submodule origin
  * repo. When relative, this URL is relative to the superproject origin
@@ -93,14 +116,16 @@ static int chop_last_dir(char **remoteurl, int is_relative)
  * the superproject working tree otherwise.
  *
  * NEEDSWORK: This works incorrectly on the domain and protocol part.
- * remote_url      url              outcome          expectation
- * http://a.com/b  ../c             http://a.com/c   as is
- * http://a.com/b/ ../c             http://a.com/c   same as previous line, but
- *                                                   ignore trailing slash in url
- * http://a.com/b  ../../c          http://c         error out
- * http://a.com/b  ../../../c       http:/c          error out
- * http://a.com/b  ../../../../c    http:c           error out
- * http://a.com/b  ../../../../../c    .:c           error out
+ * remote_url       url              outcome          expectation
+ * http://a.com/b   ../c             http://a.com/c   as is
+ * http://a.com/b/  ../c             http://a.com/c   same as previous line, but
+ *                                                    ignore trailing '/' in url
+ * http://a.com/b/. ../c             http://a.com/c   same as previous line, but
+ *                                                    ignore trailing '/.' in url
+ * http://a.com/b   ../../c          http://c         error out
+ * http://a.com/b   ../../../c       http:/c          error out
+ * http://a.com/b   ../../../../c    http:c           error out
+ * http://a.com/b   ../../../../../c    .:c           error out
  * NEEDSWORK: Given how chop_last_dir() works, this function is broken
  * when a local part has a colon in its path component, too.
  */
@@ -115,8 +140,7 @@ static char *relative_url(const char *remote_url,
 	struct strbuf sb = STRBUF_INIT;
 	size_t len = strlen(remoteurl);
 
-	if (is_dir_sep(remoteurl[len-1]))
-		remoteurl[len-1] = '\0';
+	strip_url_ending(remoteurl, &len);
 
 	if (!url_is_local_not_ssh(remoteurl) || is_absolute_path(remoteurl))
 		is_relative = 0;
@@ -149,10 +173,10 @@ static char *relative_url(const char *remote_url,
 	}
 	strbuf_reset(&sb);
 	strbuf_addf(&sb, "%s%s%s", remoteurl, colonsep ? ":" : "/", url);
-	if (ends_with(url, "/"))
-		strbuf_setlen(&sb, sb.len - 1);
 	free(remoteurl);
 
+	strip_url_ending(sb.buf, &sb.len);
+
 	if (starts_with_dot_slash(sb.buf))
 		out = xstrdup(sb.buf + 2);
 	else
diff --git a/t/t0060-path-utils.sh b/t/t0060-path-utils.sh
index 25b48e5..e154e5f 100755
--- a/t/t0060-path-utils.sh
+++ b/t/t0060-path-utils.sh
@@ -329,14 +329,17 @@ test_submodule_relative_url "(null)" "./foo" "../submodule" "submodule"
 test_submodule_relative_url "(null)" "//somewhere else/repo" "../subrepo" "//somewhere else/subrepo"
 test_submodule_relative_url "(null)" "$PWD/subsuper_update_r" "../subsubsuper_update_r" "$(pwd)/subsubsuper_update_r"
 test_submodule_relative_url "(null)" "$PWD/super_update_r2" "../subsuper_update_r" "$(pwd)/subsuper_update_r"
-test_submodule_relative_url "(null)" "$PWD/." "../." "$(pwd)/."
-test_submodule_relative_url "(null)" "$PWD" "./." "$(pwd)/."
+test_submodule_relative_url "(null)" "$PWD/sub/." "../." "$(pwd)"
+test_submodule_relative_url "(null)" "$PWD/sub/./." "../." "$(pwd)"
+test_submodule_relative_url "(null)" "$PWD/sub/.////././/./." "../." "$(pwd)"
+test_submodule_relative_url "(null)" "$PWD" "./." "$(pwd)"
 test_submodule_relative_url "(null)" "$PWD/addtest" "../repo" "$(pwd)/repo"
 test_submodule_relative_url "(null)" "$PWD" "./å äö" "$(pwd)/å äö"
-test_submodule_relative_url "(null)" "$PWD/." "../submodule" "$(pwd)/submodule"
+test_submodule_relative_url "(null)" "$PWD/sub" "../submodule" "$(pwd)/submodule"
+test_submodule_relative_url "(null)" "$PWD/sub/." "../submodule" "$(pwd)/submodule"
 test_submodule_relative_url "(null)" "$PWD/submodule" "../submodule" "$(pwd)/submodule"
 test_submodule_relative_url "(null)" "$PWD/home2/../remote" "../bundle1" "$(pwd)/home2/../bundle1"
-test_submodule_relative_url "(null)" "$PWD/submodule_update_repo" "./." "$(pwd)/submodule_update_repo/."
+test_submodule_relative_url "(null)" "$PWD/submodule_update_repo" "./." "$(pwd)/submodule_update_repo"
 test_submodule_relative_url "(null)" "file:///tmp/repo" "../subrepo" "file:///tmp/subrepo"
 test_submodule_relative_url "(null)" "foo/bar" "../submodule" "foo/submodule"
 test_submodule_relative_url "(null)" "foo" "../submodule" "submodule"

-- 
2.10.1.480.g573bd76

Junio C Hamano· Oct 18, 2016, 19:49 UTC · re: Stefan Beller · lore

Re: [PATCH] submodule--helper: normalize funny urls

Stefan Beller <sbeller@google.com> writes:

Show 24 quoted lines

> Some users may rely on this by always cloning with '/.' and having
> an additional '../' in the relative path for the submodule, and this
> patch breaks them. So why introduce this patch?
>
> The fix in c12922024 (submodule: ignore trailing slash on superproject
> URL, 2016-10-10) and prior discussion revealed, that Git and Git
> for Windows treat URLs differently, as currently Git for Windows
> strips off a trailing dot from paths when calling a Git binary
> unlike when running a shell. Which means Git for Windows is already
> doing the right thing for the case mentioned above, but it would fail
> our current tests, that test for the broken behavior and it would
> confuse users working across platforms. So we'd rather fix it
> in Git to ignore any of these trailing no ops in the path properly.
>
> We never produce the URLs with a trailing '/.' in Git ourselves,
> they come to us, because the user used it as the URL for cloning
> a superproject. Normalize these paths.
>
> Helped-by: Junio C Hamano <gitster@pobox.com>
> Signed-off-by: Stefan Beller <sbeller@google.com>
> ---
>
>  * reworded the commit message, taken from Junio, but added more explanation
>    why we want to introduce this patch.

The additional explanation is very good.

Show 11 quoted lines

> diff --git a/builtin/submodule--helper.c b/builtin/submodule--helper.c
> index 260f46f..ac03cb3 100644
> --- a/builtin/submodule--helper.c
> +++ b/builtin/submodule--helper.c
> @@ -76,6 +76,29 @@ static int chop_last_dir(char **remoteurl, int is_relative)
>  	return 0;
>  }
>  
> +static void strip_url_ending(char *url, size_t *_len)
> +{
> +	size_t len = _len ? *_len : strlen(url);

Stare at our codebase and you'd notice that we avoid using names with leading underscore deliberately and use trailing one instead when we name a throw-away name like this. Let's do the same here. I.e.

	static void strip_url_ending(char *url, size_t *len_)
	{
		size_t len = len_ ? *len_ : strlen(url);

> +	for (;;) {
> +		if (len > 1 && is_dir_sep(url[len-2]) && url[len-1] == '.') {
> +			url[len-2] = '\0';

"len-1" and "len-2" are usually spelled with SP on both sides of binary operators.

Show 6 quoted lines

> +			len -= 2;
> +			continue;
> +		}
> +		if (len > 0 && is_dir_sep(url[len-1])) {
> +			url[len-1] = '\0';
> +			len --;

And post-decrement sticks to whatever it is decrementing without SP.

> +			continue;
> +		}

patchsubmodule--helper: normalize funny urls