[RFC/PATCH] Detailed diagnostic when parsing an object name fails.

[RFC/PATCH] Detailed diagnostic when parsing an object name fails.

[Matthieu Moy]

The previous error message was the same in many situations (unknown
revision or path not in the working tree). We try to help the user as
much as possible to understand the error, especially with the
sha1:filename notation. In this case, we say whether the sha1 or the
filename is problematic, and diagnose the confusion between
relative-to-root and relative-to-$PWD confusion precisely.

Signed-off-by: Matthieu Moy <Matthieu.Moy@imag.fr>
---

The original motivation is actually to anwser the FAQ of "git show
HEAD:foo.txt" being relative to the root, while some users would
expect it relative to $PWD but the patch ended up being far more
general. At least, 

$ cd git
$ cd t
$ ../git show HEAD:test-lib.sh 
fatal: Path 't/test-lib.sh' exists, but not 'test-lib.sh'.
Did you mean 'HEAD:t/test-lib.sh'?

A few remarks/RFH:

* It's my first time playing with the index API, so my
  diagnose_invalid_index_path may be incorrect/suboptimal/...

* This definitely requires a few test-cases, but I don't have time for
  it right now.

* Is my way of having default arguments for get_sha1_with_mode OK with
  the usual coding style of Git?

 cache.h     |    6 +++-
 setup.c     |   15 +++++++++-
 sha1_name.c |   87 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++---
 3 files changed, 101 insertions(+), 7 deletions(-)

diff --git a/cache.h b/cache.h
index 0e69384..5c8cb5f 100644
--- a/cache.h
+++ b/cache.h
@@ -708,7 +708,11 @@ static inline unsigned int hexval(unsigned char c)
 #define DEFAULT_ABBREV 7
 
 extern int get_sha1(const char *str, unsigned char *sha1);
-extern int get_sha1_with_mode(const char *str, unsigned char *sha1, unsigned *mode);
+static inline get_sha1_with_mode(const char *str, unsigned char *sha1, unsigned *mode)
+{
+	return get_sha1_with_mode_1(str, sha1, mode, 0, NULL);
+}
+extern int get_sha1_with_mode_1(const char *str, unsigned char *sha1, unsigned *mode, int fatal, const char *prefix);
 extern int get_sha1_hex(const char *hex, unsigned char *sha1);
 extern char *sha1_to_hex(const unsigned char *sha1);	/* static buffer result! */
 extern int read_ref(const char *filename, unsigned char *sha1);
diff --git a/setup.c b/setup.c
index f67250b..3094e8b 100644
--- a/setup.c
+++ b/setup.c
@@ -74,6 +74,18 @@ int check_filename(const char *prefix, const char *arg)
 	die_errno("failed to stat '%s'", arg);
 }
 
+static void NORETURN die_verify_filename(const char *prefix, const char *arg)
+{
+	unsigned char sha1[20];
+	unsigned mode;
+	/* try a detailed diagnostic ... */
+	get_sha1_with_mode_1(arg, sha1, &mode, 1, prefix);
+	/* ... or fall back the most general message. */
+	die("ambiguous argument '%s': unknown revision or path not in the working tree.\n"
+	    "Use '--' to separate paths from revisions", arg);
+
+}
+
 /*
  * Verify a filename that we got as an argument for a pathspec
  * entry. Note that a filename that begins with "-" never verifies
@@ -87,8 +99,7 @@ void verify_filename(const char *prefix, const char *arg)
 		die("bad flag '%s' used after filename", arg);
 	if (check_filename(prefix, arg))
 		return;
-	die("ambiguous argument '%s': unknown revision or path not in the working tree.\n"
-	    "Use '--' to separate paths from revisions", arg);
+	die_verify_filename(prefix, arg);
 }
 
 /*
diff --git a/sha1_name.c b/sha1_name.c
index 44bb62d..172c128 100644
--- a/sha1_name.c
+++ b/sha1_name.c
@@ -804,7 +804,69 @@ int get_sha1(const char *name, unsigned char *sha1)
 	return get_sha1_with_mode(name, sha1, &unused);
 }
 
-int get_sha1_with_mode(const char *name, unsigned char *sha1, unsigned *mode)
+static void diagnose_invalid_sha1_path(const char *prefix,
+				       const char *filename,
+				       const char *tree_sha1,
+				       const char *object_name)
+{
+	struct stat st;
+	unsigned char sha1[20];
+	unsigned mode;
+
+	if (!lstat(filename, &st))
+		die("Path '%s' exists on disk, but not in '%s'.",
+		    filename, object_name);
+	if (errno == ENOENT || errno == ENOTDIR) {
+		char *fullname = malloc(strlen(filename)
+					     + strlen(prefix) + 1);
+		strcpy(fullname, prefix);
+		strcat(fullname, filename);
+
+		if (!get_tree_entry(tree_sha1, fullname,
+				    sha1, &mode)) {
+			die("Path '%s' exists, but not '%s'.\n"
+			    "Did you mean '%s:%s'?",
+			    fullname,
+			    filename,
+			    object_name,
+			    fullname);
+		}
+		die("Path '%s' does not exist in '%s'",
+		    filename, object_name);
+	}
+}
+
+static void diagnose_invalid_index_path(int stage,
+					const char *prefix,
+					const char *filename)
+{
+	struct stat st;
+	if (!lstat(filename, &st))
+		die("Path '%s' exists on disk, but not in the index.", filename);
+	if (errno == ENOENT || errno == ENOTDIR) {
+		struct cache_entry *ce;
+		int pos;
+		int namelen = strlen(filename) + strlen(prefix);
+		char *fullname = malloc(namelen + 1);
+		strcpy(fullname, prefix);
+		strcat(fullname, filename);
+		pos = cache_name_pos(fullname, namelen);
+		if (pos < 0)
+			pos = -pos - 1;
+		ce = active_cache[pos];
+		if (ce_namelen(ce) == namelen &&
+		    !memcmp(ce->name, fullname, namelen))
+			die("Path '%s' is in the index, but not '%s'.\n"
+			    "Did you mean ':%d:%s'?",
+			    fullname, filename,
+			    stage, fullname);
+
+		die("Path '%s' does not exist (either on disk or in the index).", filename);
+	}
+}
+
+
+int get_sha1_with_mode_1(const char *name, unsigned char *sha1, unsigned *mode, int fatal, const char *prefix)
 {
 	int ret, bracket_depth;
 	int namelen = strlen(name);
@@ -850,6 +912,8 @@ int get_sha1_with_mode(const char *name, unsigned char *sha1, unsigned *mode)
 			}
 			pos++;
 		}
+		if (fatal)
+			diagnose_invalid_index_path(stage, prefix, cp);
 		return -1;
 	}
 	for (cp = name, bracket_depth = 0; *cp; cp++) {
@@ -862,9 +926,24 @@ int get_sha1_with_mode(const char *name, unsigned char *sha1, unsigned *mode)
 	}
 	if (*cp == ':') {
 		unsigned char tree_sha1[20];
-		if (!get_sha1_1(name, cp-name, tree_sha1))
-			return get_tree_entry(tree_sha1, cp+1, sha1,
-					      mode);
+		char *object_name;
+		if (fatal) {
+			object_name = malloc(cp-name+1);
+			strncpy(object_name, name, cp-name);
+			object_name[cp-name] = '\0';
+		}
+		if (!get_sha1_1(name, cp-name, tree_sha1)) {
+			const char *filename = cp+1;
+			ret = get_tree_entry(tree_sha1, filename, sha1, mode);
+			if (fatal)
+				diagnose_invalid_sha1_path(prefix, filename,
+							   tree_sha1, object_name);
+
+			return ret;
+		} else {
+			if (fatal)
+				die("Invalid object name '%s'.", object_name);
+		}
 	}
 	return ret;
 }
-- 
1.6.6.rc0.256.g6060

Re: [RFC/PATCH] Detailed diagnostic when parsing an object name fails.

[Junio C Hamano]

Matthieu Moy <Matthieu.Moy@imag.fr> writes:

> The original motivation is actually to anwser the FAQ of "git show
> HEAD:foo.txt" being relative to the root, while some users would
> expect it relative to $PWD but the patch ended up being far more
> general. At least, 
>
> $ cd git
> $ cd t
> $ ../git show HEAD:test-lib.sh 
> fatal: Path 't/test-lib.sh' exists, but not 'test-lib.sh'.
> Did you mean 'HEAD:t/test-lib.sh'?

The first thought that comes to mind is that if it makes more sense to
just fall back to the interpretation of the input when the tool has
already figured out to second guess the intention of the user like the
above message does.

That would obviously break scripts that try to make sure the _absense_ of
a path in a tree-ish (or in the index if you lack "HEAD" in your example),
expecting:

   git rev-parse HEAD:test-lib.sh ||
   echo "test-lib.sh shouldn't be at the top level"

to work regardless of where you are in the work tree, so it won't fly
well.

Perhaps the second step would be to teach the machinery to understand a
syntax like "<tree-ish>:./<path>" and have it prefix the path to the
current subdirectory from the root of the work tree, and with such an
enhancement, the suggestion given by this patch would probably change to
"Did you mean 'HEAD:./test-lib.sh'?", but that would be a separate topic.

Re: [RFC/PATCH] Detailed diagnostic when parsing an object name fails.

[Matthieu Moy]

Junio C Hamano <gitster@pobox.com> writes:

>> $ ../git show HEAD:test-lib.sh 
>> fatal: Path 't/test-lib.sh' exists, but not 'test-lib.sh'.
>> Did you mean 'HEAD:t/test-lib.sh'?
>
> The first thought that comes to mind is that if it makes more sense to
> just fall back to the interpretation of the input when the tool has
> already figured out to second guess the intention of the user like the
> above message does.
>
> That would obviously break scripts that try to make sure the _absense_ of
> a path in a tree-ish (or in the index if you lack "HEAD" in your example),
> expecting:
>
>    git rev-parse HEAD:test-lib.sh ||
>    echo "test-lib.sh shouldn't be at the top level"

There's another (more important IMO) problem: if HEAD contains both
file.txt and subdir/file.txt, then what should

cd subdir
git show HEAD:file.txt

do? Allowing HEAD:file-in-a-subdirectory.txt would indirectly mean
teaching users to use in, and they'd be bitten by an ambiguous
behavior one day or another ...

> Perhaps the second step would be to teach the machinery to understand a
> syntax like "<tree-ish>:./<path>" and have it prefix the path to the
> current subdirectory from the root of the work tree, and with such an
> enhancement, the suggestion given by this patch would probably change to
> "Did you mean 'HEAD:./test-lib.sh'?", but that would be a separate
> topic.

Exactly. I think this HEAD:./relative-path syntax has been discussed
here already, but I don't remember the outcome of the discussion. If
it's ever implemented, my patch, modified as you suggest will help
users to discover the feature ;-).

BTW, I finally had time to write a test. Current version below FYI
(fixed a segfault discovered by testing too), but I'll resend properly
when I get enough feedback.


>From 1bc1c8d114b538f57a5ba4a501436229d644d587 Mon Sep 17 00:00:00 2001
From: Matthieu Moy <Matthieu.Moy@imag.fr>
Date: Mon, 30 Nov 2009 17:32:39 +0100
Subject: [PATCH] Detailed diagnosis when parsing an object name fails.

The previous error message was the same in many situations (unknown
revision or path not in the working tree). We try to help the user as
much as possible to understand the error, especially with the
sha1:filename notation. In this case, we say whether the sha1 or the
filename is problematic, and diagnose the confusion between
relative-to-root and relative-to-$PWD confusion precisely.

The 6 new error messages are tested.
---
 cache.h                        |    6 ++-
 setup.c                        |   15 +++++-
 sha1_name.c                    |   95 ++++++++++++++++++++++++++++++++++++++--
 t/t1506-rev-parse-diagnosis.sh |   67 ++++++++++++++++++++++++++++
 4 files changed, 176 insertions(+), 7 deletions(-)
 create mode 100755 t/t1506-rev-parse-diagnosis.sh

diff --git a/cache.h b/cache.h
index 0e69384..5c8cb5f 100644
--- a/cache.h
+++ b/cache.h
@@ -708,7 +708,11 @@ static inline unsigned int hexval(unsigned char c)
 #define DEFAULT_ABBREV 7
 
 extern int get_sha1(const char *str, unsigned char *sha1);
-extern int get_sha1_with_mode(const char *str, unsigned char *sha1, unsigned *mode);
+static inline get_sha1_with_mode(const char *str, unsigned char *sha1, unsigned *mode)
+{
+	return get_sha1_with_mode_1(str, sha1, mode, 0, NULL);
+}
+extern int get_sha1_with_mode_1(const char *str, unsigned char *sha1, unsigned *mode, int fatal, const char *prefix);
 extern int get_sha1_hex(const char *hex, unsigned char *sha1);
 extern char *sha1_to_hex(const unsigned char *sha1);	/* static buffer result! */
 extern int read_ref(const char *filename, unsigned char *sha1);
diff --git a/setup.c b/setup.c
index f67250b..3094e8b 100644
--- a/setup.c
+++ b/setup.c
@@ -74,6 +74,18 @@ int check_filename(const char *prefix, const char *arg)
 	die_errno("failed to stat '%s'", arg);
 }
 
+static void NORETURN die_verify_filename(const char *prefix, const char *arg)
+{
+	unsigned char sha1[20];
+	unsigned mode;
+	/* try a detailed diagnostic ... */
+	get_sha1_with_mode_1(arg, sha1, &mode, 1, prefix);
+	/* ... or fall back the most general message. */
+	die("ambiguous argument '%s': unknown revision or path not in the working tree.\n"
+	    "Use '--' to separate paths from revisions", arg);
+
+}
+
 /*
  * Verify a filename that we got as an argument for a pathspec
  * entry. Note that a filename that begins with "-" never verifies
@@ -87,8 +99,7 @@ void verify_filename(const char *prefix, const char *arg)
 		die("bad flag '%s' used after filename", arg);
 	if (check_filename(prefix, arg))
 		return;
-	die("ambiguous argument '%s': unknown revision or path not in the working tree.\n"
-	    "Use '--' to separate paths from revisions", arg);
+	die_verify_filename(prefix, arg);
 }
 
 /*
diff --git a/sha1_name.c b/sha1_name.c
index 44bb62d..030e2ac 100644
--- a/sha1_name.c
+++ b/sha1_name.c
@@ -804,7 +804,77 @@ int get_sha1(const char *name, unsigned char *sha1)
 	return get_sha1_with_mode(name, sha1, &unused);
 }
 
-int get_sha1_with_mode(const char *name, unsigned char *sha1, unsigned *mode)
+static void diagnose_invalid_sha1_path(const char *prefix,
+				       const char *filename,
+				       const char *tree_sha1,
+				       const char *object_name)
+{
+	struct stat st;
+	unsigned char sha1[20];
+	unsigned mode;
+
+	if (!prefix)
+		prefix = "";
+
+	if (!lstat(filename, &st))
+		die("Path '%s' exists on disk, but not in '%s'.",
+		    filename, object_name);
+	if (errno == ENOENT || errno == ENOTDIR) {
+		char *fullname = malloc(strlen(filename)
+					     + strlen(prefix) + 1);
+		strcpy(fullname, prefix);
+		strcat(fullname, filename);
+
+		if (!get_tree_entry(tree_sha1, fullname,
+				    sha1, &mode)) {
+			die("Path '%s' exists, but not '%s'.\n"
+			    "Did you mean '%s:%s'?",
+			    fullname,
+			    filename,
+			    object_name,
+			    fullname);
+		}
+		die("Path '%s' does not exist in '%s'",
+		    filename, object_name);
+	}
+}
+
+static void diagnose_invalid_index_path(int stage,
+					const char *prefix,
+					const char *filename)
+{
+	struct stat st;
+
+	if (!prefix)
+		prefix = "";
+
+	if (!lstat(filename, &st))
+		die("Path '%s' exists on disk, but not in the index.", filename);
+	if (errno == ENOENT || errno == ENOTDIR) {
+		struct cache_entry *ce;
+		int pos;
+		int namelen = strlen(filename) + strlen(prefix);
+		char *fullname = malloc(namelen + 1);
+		strcpy(fullname, prefix);
+		strcat(fullname, filename);
+		pos = cache_name_pos(fullname, namelen);
+		if (pos < 0)
+			pos = -pos - 1;
+		ce = active_cache[pos];
+		if (ce_namelen(ce) == namelen &&
+		    !memcmp(ce->name, fullname, namelen))
+			die("Path '%s' is in the index, but not '%s'.\n"
+			    "Did you mean ':%d:%s'?",
+			    fullname, filename,
+			    stage, fullname);
+
+		die("Path '%s' does not exist (neither on disk nor in the index).",
+		    filename);
+	}
+}
+
+
+int get_sha1_with_mode_1(const char *name, unsigned char *sha1, unsigned *mode, int fatal, const char *prefix)
 {
 	int ret, bracket_depth;
 	int namelen = strlen(name);
@@ -850,6 +920,8 @@ int get_sha1_with_mode(const char *name, unsigned char *sha1, unsigned *mode)
 			}
 			pos++;
 		}
+		if (fatal)
+			diagnose_invalid_index_path(stage, prefix, cp);
 		return -1;
 	}
 	for (cp = name, bracket_depth = 0; *cp; cp++) {
@@ -862,9 +934,24 @@ int get_sha1_with_mode(const char *name, unsigned char *sha1, unsigned *mode)
 	}
 	if (*cp == ':') {
 		unsigned char tree_sha1[20];
-		if (!get_sha1_1(name, cp-name, tree_sha1))
-			return get_tree_entry(tree_sha1, cp+1, sha1,
-					      mode);
+		char *object_name;
+		if (fatal) {
+			object_name = malloc(cp-name+1);
+			strncpy(object_name, name, cp-name);
+			object_name[cp-name] = '\0';
+		}
+		if (!get_sha1_1(name, cp-name, tree_sha1)) {
+			const char *filename = cp+1;
+			ret = get_tree_entry(tree_sha1, filename, sha1, mode);
+			if (fatal)
+				diagnose_invalid_sha1_path(prefix, filename,
+							   tree_sha1, object_name);
+
+			return ret;
+		} else {
+			if (fatal)
+				die("Invalid object name '%s'.", object_name);
+		}
 	}
 	return ret;
 }
diff --git a/t/t1506-rev-parse-diagnosis.sh b/t/t1506-rev-parse-diagnosis.sh
new file mode 100755
index 0000000..8112d56
--- /dev/null
+++ b/t/t1506-rev-parse-diagnosis.sh
@@ -0,0 +1,67 @@
+#!/bin/sh
+
+test_description='test git rev-parse diagnosis for invalid argument'
+
+exec </dev/null
+
+. ./test-lib.sh
+
+HASH_file=
+
+test_expect_success 'set up basic repo' '
+	echo one > file.txt &&
+	mkdir subdir &&
+	echo two > subdir/file.txt &&
+	echo three > subdir/file2.txt &&
+	git add . &&
+	git commit -m init &&
+	echo four > index-only.txt &&
+	git add index-only.txt &&
+	echo five > disk-only.txt
+'
+
+test_expect_success 'correct file objects' '
+	HASH_file=$(git rev-parse HEAD:file.txt) &&
+	git rev-parse HEAD:subdir/file.txt &&
+	git rev-parse :index-only.txt &&
+	cd subdir &&
+	git rev-parse HEAD:file.txt &&
+	git rev-parse HEAD:subdir/file2.txt &&
+	test $HASH_file = $(git rev-parse HEAD:file.txt) &&
+	test $HASH_file = $(git rev-parse :file.txt) &&
+	test $HASH_file = $(git rev-parse :0:file.txt) &&
+	cd ..
+'
+
+test_expect_success 'incorrect revision id' '
+	test_must_fail git rev-parse foobar:file.txt 2>&1 |
+		grep "Invalid object name '"'"'foobar'"'"'." &&
+	test_must_fail git rev-parse foobar 2>&1 |
+		grep "unknown revision or path not in the working tree."
+'
+
+test_expect_success 'incorrect file in sha1:path' '
+	test_must_fail git rev-parse HEAD:nothing.txt 2>&1 |
+		grep "fatal: Path '"'"'nothing.txt'"'"' does not exist in '"'"'HEAD'"'"'" &&
+	test_must_fail git rev-parse HEAD:index-only.txt 2>&1 |
+		grep "fatal: Path '"'"'index-only.txt'"'"' exists on disk, but not in '"'"'HEAD'"'"'." &&
+	cd subdir &&
+	test_must_fail git rev-parse HEAD:file2.txt 2>&1 |
+		grep "Did you mean '"'"'HEAD:subdir/file2.txt'"'"'?" &&
+	cd ..
+'
+
+test_expect_success 'incorrect file in :path and :0:path' '
+	test_must_fail git rev-parse :nothing.txt 2>&1 |
+		grep "fatal: Path '"'"'nothing.txt'"'"' does not exist (neither on disk nor in the index)." &&
+	test_must_fail git rev-parse :1:nothing.txt 2>&1 |
+		grep "Path '"'"'nothing.txt'"'"' does not exist (neither on disk nor in the index)." &&
+	cd subdir &&
+	test_must_fail git rev-parse :file2.txt 2>&1 |
+		grep "Did you mean '"'"':0:subdir/file2.txt'"'"'?" &&
+	cd .. &&
+	test_must_fail git rev-parse :disk-only.txt 2>&1 |
+		grep "fatal: Path '"'"'disk-only.txt'"'"' exists on disk, but not in the index."
+'
+
+test_done
-- 
1.6.6.rc0.256.g6060


--
Matthieu Moy
http://www-verimag.imag.fr/~moy/

Re: [RFC/PATCH] Detailed diagnostic when parsing an object name fails.

[Matthieu Moy]

Matthieu Moy <Matthieu.Moy@grenoble-inp.fr> writes:

>> Perhaps the second step would be to teach the machinery to understand a
>> syntax like "<tree-ish>:./<path>" and have it prefix the path to the
>> current subdirectory from the root of the work tree, and with such an
>> enhancement, the suggestion given by this patch would probably change to
>> "Did you mean 'HEAD:./test-lib.sh'?", but that would be a separate
>> topic.
>
> Exactly. I think this HEAD:./relative-path syntax has been discussed
> here already, but I don't remember the outcome of the discussion. If
> it's ever implemented, my patch, modified as you suggest will help
> users to discover the feature ;-).

I gave it a try, and it seems it's not as easy to implement as it
seems.

The main task is to teach get_sha1_with_mode_1(..., prefix, ...) to
notice a ./ in "HEAD:./filename", and to replace it with prefix, which
is easy. The problem is to get "prefix" reliably. Since
get_sha1_with_mode_1 is called by get_sha1, which doesn't know about
prefix, and which is called from at least 92 places in the code, this
would require changing all these calls to add the "prefix" argument
(and to find out where to get this prefix from).

So, I guess I'll give up :-(. (unless someone either show a great
motivation for the feature, or a magic formula to make the patch
short)

FYI, here's the toy patch I started (works for "git show HEAD:./file",
but not for "git rev-parse HEAD:./file" for example):

diff --git a/cache.h b/cache.h
index c122bfa..a44f06f 100644
--- a/cache.h
+++ b/cache.h
@@ -708,10 +708,10 @@ static inline unsigned int hexval(unsigned char c)
 #define DEFAULT_ABBREV 7
 
 extern int get_sha1(const char *str, unsigned char *sha1);
-extern int get_sha1_with_mode_1(const char *str, unsigned char *sha1, unsigned *mode, int gently, const char *prefix);
-static inline int get_sha1_with_mode(const char *str, unsigned char *sha1, unsigned *mode)
+extern int get_sha1_with_mode_1(const char *str, unsigned char *sha1, unsigned *mode, const char *prefix, int gently);
+static inline int get_sha1_with_mode(const char *str, unsigned char *sha1, unsigned *mode, const char *prefix)
 {
-	return get_sha1_with_mode_1(str, sha1, mode, 1, NULL);
+	return get_sha1_with_mode_1(str, sha1, mode, prefix, 1);
 }
 extern int get_sha1_hex(const char *hex, unsigned char *sha1);
 extern char *sha1_to_hex(const unsigned char *sha1);	/* static buffer result! */
diff --git a/revision.c b/revision.c
index 25fa14d..19ddb21 100644
--- a/revision.c
+++ b/revision.c
@@ -944,7 +944,7 @@ int handle_revision_arg(const char *arg, struct rev_info *revs,
 		local_flags = UNINTERESTING;
 		arg++;
 	}
-	if (get_sha1_with_mode(arg, sha1, &mode))
+	if (get_sha1_with_mode(arg, sha1, &mode, revs->prefix))
 		return -1;
 	if (!cant_be_filename)
 		verify_non_filename(revs->prefix, arg);
@@ -1419,7 +1419,7 @@ int setup_revisions(int argc, const char **argv, struct rev_info *revs, const ch
 		unsigned char sha1[20];
 		struct object *object;
 		unsigned mode;
-		if (get_sha1_with_mode(revs->def, sha1, &mode))
+		if (get_sha1_with_mode(revs->def, sha1, &mode, revs->prefix))
 			die("bad default revision '%s'", revs->def);
 		object = get_reference(revs, revs->def, sha1, 0);
 		add_pending_object_with_mode(revs, object, revs->def, mode);
diff --git a/setup.c b/setup.c
index 5792eb7..60c1e08 100644
--- a/setup.c
+++ b/setup.c
@@ -79,7 +79,7 @@ static void NORETURN die_verify_filename(const char *prefix, const char *arg)
 	unsigned char sha1[20];
 	unsigned mode;
 	/* try a detailed diagnostic ... */
-	get_sha1_with_mode_1(arg, sha1, &mode, 0, prefix);
+	get_sha1_with_mode_1(arg, sha1, &mode, prefix, 0);
 	/* ... or fall back the most general message. */
 	die("ambiguous argument '%s': unknown revision or path not in the working tree.\n"
 	    "Use '--' to separate paths from revisions", arg);
diff --git a/sha1_name.c b/sha1_name.c
index ca8f9db..330d3fe 100644
--- a/sha1_name.c
+++ b/sha1_name.c
@@ -801,7 +801,7 @@ release_return:
 int get_sha1(const char *name, unsigned char *sha1)
 {
 	unsigned unused;
-	return get_sha1_with_mode(name, sha1, &unused);
+	return get_sha1_with_mode(name, sha1, &unused, NULL);
 }
 
 /* Must be called only when object_name:filename doesn't exist. */
@@ -893,7 +893,7 @@ static void diagnose_invalid_index_path(int stage,
 }
 
 
-int get_sha1_with_mode_1(const char *name, unsigned char *sha1, unsigned *mode, int gently, const char *prefix)
+int get_sha1_with_mode_1(const char *name, unsigned char *sha1, unsigned *mode, const char *prefix, int gently)
 {
 	int ret, bracket_depth;
 	int namelen = strlen(name);
@@ -961,11 +961,26 @@ int get_sha1_with_mode_1(const char *name, unsigned char *sha1, unsigned *mode,
 		}
 		if (!get_sha1_1(name, cp-name, tree_sha1)) {
 			const char *filename = cp+1;
-			ret = get_tree_entry(tree_sha1, filename, sha1, mode);
-			if (!gently) {
-				diagnose_invalid_sha1_path(prefix, filename,
-							   tree_sha1, object_name);
-				free(object_name);
+			if (filename[0] == '.' && filename[1] == '/') {
+				if (!prefix)
+					prefix = "";
+				char *absfilename = xmalloc((strlen(filename) - 2)
+							    + strlen(prefix) + 1);
+				strcpy(absfilename, prefix);
+				strcat(absfilename, filename+2);
+				ret = get_tree_entry(tree_sha1, absfilename, sha1, mode);
+				if (!gently) {
+					diagnose_invalid_sha1_path(prefix, absfilename,
+								   tree_sha1, object_name);
+					free(object_name);
+				}
+			} else {
+				ret = get_tree_entry(tree_sha1, filename, sha1, mode);
+				if (!gently) {
+					diagnose_invalid_sha1_path(prefix, filename,
+								   tree_sha1, object_name);
+					free(object_name);
+				}
 			}
 			return ret;
 		} else {


-- 
Matthieu Moy
http://www-verimag.imag.fr/~moy/