In Git for Windows, we ran with a patch "in production" for quite a while
where paths starting with a slash (i.e. looking like Unix paths, not like
Windows paths) were interpreted as being relative to the runtime prefix,
when expanded via expand_user_path().
This was sent to the Git mailing list as a discussion starter, and it was
pointed out that this is neither portable nor unambiguous.
After the dust settled, I thought about the presented ideas for a while
(quite a while...), and ended up with the following: any path starting with
<RUNTIME-PREFIX>/ is expanded. This is ambiguous because it could be a valid
path. But then, it is unlikely, and if someone really wants to specify such
a path, it is easy to slap a ./ in front and they're done.
Changes since v1:
* Included a test for the RUNTIME_PREFIX that I had meant to send for ages
already, and based on which...
* A test case was added to verify that this actually works as intended
* It is no longer Windows-specific
* I added some documentation
Johannes Schindelin (2):
tests: exercise the RUNTIME_PREFIX feature
expand_user_path(): support specifying paths relative to the runtime
prefix
Documentation/config.txt | 10 ++++++++++
Makefile | 5 +++++
path.c | 5 +++++
t/t0060-path-utils.sh | 26 ++++++++++++++++++++++++++
4 files changed, 46 insertions(+)
base-commit: ebf3c04b262aa27fbb97f8a0156c2347fecafafb
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-66%2Fdscho%2Fmingw-expand-absolute-user-path-v2
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-66/dscho/mingw-expand-absolute-user-path-v2
Pull-Request: https://github.com/gitgitgadget/git/pull/66
Range-diff vs v1:
-: ----------- > 1: cc8f09baba9 tests: exercise the RUNTIME_PREFIX feature
1: 2287dd96cf0 ! 2: 66df56f5db0 mingw: handle absolute paths in expand_user_path()
@@ Metadata
Author: Johannes Schindelin <Johannes.Schindelin@xxxxxx>
## Commit message ##
- mingw: handle absolute paths in expand_user_path()
+ expand_user_path(): support specifying paths relative to the runtime prefix
- On Windows, an absolute POSIX path needs to be turned into a Windows
- one.
+ Ever since Git learned to detect its install location at runtime, there
+ was the slightly awkward problem that it was impossible to specify paths
+ relative to said location.
+
+ For example, if a version of Git was shipped with custom SSL
+ certificates to use, there was no portable way to specify
+ `http.sslCAInfo`.
+
+ In Git for Windows, the problem was "solved" for years by interpreting
+ paths starting with a slash as relative to the runtime prefix.
+
+ However, this is not correct: such paths _are_ legal on Windows, and
+ they are interpreted as absolute paths in the same drive as the current
+ directory.
+
+ After a lengthy discussion, and a way lengthier time to mull over the
+ problem and its best solution, we decided to introduce support for the
+ magic sequence `<RUNTIME-PREFIX>/`. If a path starts with this, the
+ remainder is interpreted as relative to the detected runtime prefix.
+
+ This solves the problem, but what new problems does it stir up? Here are
+ the two most obvious ones:
+
+ - What if Git was not compiled with support for a runtime prefix?
+
+ In that case, we will simply use the compiled-in hard-coded prefix.
+
+ - What if a user _wants_ to specify a path starting with the magic
+ sequence?
+
+ In that case, the user will simply need to prefix the magic sequence
+ with `./` and voilà, the path won't be expanded.
Signed-off-by: Johannes Schindelin <johannes.schindelin@xxxxxx>
+ ## Documentation/config.txt ##
+@@ Documentation/config.txt: pathname::
+ tilde expansion happens to such a string: `~/`
+ is expanded to the value of `$HOME`, and `~user/` to the
+ specified user's home directory.
+++
++If a path starts with `<RUNTIME-PREFIX>/`, the remainder is
++interpreted as a path relative to Git's "runtime prefix", i.e. relative
++to the location where Git itself was installed. For example,
++`<RUNTIME-PREFIX>/bin/` refers to the directory in which the Git
++executable itself lives. If Git was compiled without runtime prefix
++support, the compiled-in prefix will be subsituted instead. In the
++unlikely event that a literal path needs to be specified that should
++_not_ be expanded, it needs to be prefixed by `./`, like so:
++`./<RUNTIME-PREFIX>/bin`.
+
+
+ Variables
+
## path.c ##
@@
- #include "path.h"
#include "packfile.h"
#include "object-store.h"
+ #include "lockfile.h"
+#include "exec-cmd.h"
static int get_st_mode_bits(const char *path, int *mode)
@@ path.c: char *expand_user_path(const char *path, int real_home)
if (path == NULL)
goto return_null;
-+#ifdef __MINGW32__
-+ if (path[0] == '/')
-+ return system_path(path + 1);
-+#endif
++
++ if (skip_prefix(path, "<RUNTIME-PREFIX>/", &path))
++ return system_path(path);
++
if (path[0] == '~') {
const char *first_slash = strchrnul(path, '/');
const char *username = path + 1;
+
+ ## t/t0060-path-utils.sh ##
+@@ t/t0060-path-utils.sh: test_expect_success RUNTIME_PREFIX,CAN_EXEC_IN_PWD 'RUNTIME_PREFIX works' '
+ cp "$GIT_EXEC_PATH"/git$X pretend/bin/ &&
+ GIT_EXEC_PATH= ./pretend/bin/git here >actual &&
+ echo HERE >expect &&
++ test_cmp expect actual'
++
++test_expect_success RUNTIME_PREFIX,CAN_EXEC_IN_PWD '<RUNTIME-PREFIX>/ works' '
++ mkdir -p pretend/bin &&
++ cp "$GIT_EXEC_PATH"/git$X pretend/bin/ &&
++ git config yes.path "<RUNTIME-PREFIX>/yes" &&
++ GIT_EXEC_PATH= ./pretend/bin/git config --path yes.path >actual &&
++ echo "$(pwd)/pretend/yes" >expect &&
+ test_cmp expect actual
+ '
+
--
gitgitgadget
