[PATCH 2/3] Fix .git/ discovery at the root of UNC shares

From: Johannes Schindelin via GitGitGadget <gitgitgadget@gmail.com>
Date: Aug 24, 2019, 22:10 UTC
Message-ID: <e27a58d363c11c941a1e7b921dae8487a9d062df.1566684643.git.gitgitgadget@gmail.com>
In-Reply-To: <pull.141.git.gitgitgadget@gmail.com>

From: Johannes Schindelin <johannes.schindelin@gmx.de>

A very common assumption in Git's source code base is that offset_1st_component() returns either 0 for relative paths, or 1 for absolute paths that start with a slash. In other words, the return value is either 0 or points just after the dir separator.

This assumption is not fulfilled when calling offset_1st_component() e.g. on UNC paths on Windows, e.g. "//my-server/my-share". In this case, offset_1st_component() returns the length of the entire string (which is correct, because stripping the last "component" would not result in a valid directory), yet the return value still does not point just after a dir separator.

This assumption is most prominently seen in the setup_git_directory_gently_1() function, where we want to append a ".git" component and simply assume that there is already a dir separator. In the UNC example given above, this assumption is incorrect.

As a consequence, Git will fail to handle a worktree at the top of a UNC share correctly.

Let's fix this by adding a dir separator specifically for that case: we found that there is no first component in the path and it does not end in a dir separator? Then add it.

This fixes https://github.com/git-for-windows/git/issues/1320

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
---
 setup.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/setup.c b/setup.c
index a803b3ade3..3d24de15dd 100644
--- a/setup.c
+++ b/setup.c
@@ -934,6 +934,12 @@ static enum discovery_result setup_git_directory_gently_1(struct strbuf *dir,
 	if (ceil_offset < 0)
 		ceil_offset = min_offset - 2;
 
+	if (min_offset && min_offset == dir->len &&
+	    !is_dir_sep(dir->buf[min_offset - 1])) {
+		strbuf_addch(dir, '/');
+		min_offset++;
+	}
+
 	/*
 	 * Test in the following order (relative to the dir):
 	 * - .git (file containing "gitdir: <path>")

-- 
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