Trace into open fd and refactor tracing code.

Now if GIT_TRACE is set to an integer value greater than 1
and lower than 10, we interpret this as an open fd value
and we trace into it. Note that this behavior is not
compatible with the previous one.

We also trace whole messages using one write(2) call to
make sure messages from processes do net get mixed up in
the middle.

It's now possible to run the tests like this:

	GIT_TRACE=9 make test 9>/var/tmp/trace.log

Signed-off-by: Christian Couder <chriscool@tuxfamily.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>

10 files changed, 196 insertions, 64 deletions

diff --git a/Makefile b/Makefile
index 05bd77f967..a639cdfcfb 100644
--- a/Makefile
+++ b/Makefile
@@ -249,7 +249,7 @@ LIB_OBJS = \
 	server-info.o setup.o sha1_file.o sha1_name.o strbuf.o \
 	tag.o tree.o usage.o config.o environment.o ctype.o copy.o \
 	fetch-clone.o revision.o pager.o tree-walk.o xdiff-interface.o \
-	write_or_die.o \
+	write_or_die.o trace.o \
 	alloc.o merge-file.o path-list.o help.o unpack-trees.o $(DIFF_OBJS)
 
 BUILTIN_OBJS = \
diff --git a/cache.h b/cache.h
index 03d9dd0488..f532b46515 100644
--- a/cache.h
+++ b/cache.h
@@ -398,6 +398,7 @@ extern char git_commit_encoding[MAX_ENCODING_LENGTH];
 
 extern int copy_fd(int ifd, int ofd);
 extern void write_or_die(int fd, const void *buf, size_t count);
+extern int write_or_whine(int fd, const void *buf, size_t count, const char *msg);
 
 /* Finish off pack transfer receiving end */
 extern int receive_unpack_pack(int fd[2], const char *me, int quiet, int);
@@ -423,4 +424,9 @@ extern struct commit *alloc_commit_node(void);
 extern struct tag *alloc_tag_node(void);
 extern void alloc_report(void);
 
+/* trace.c */
+extern int nfvasprintf(char **str, const char *fmt, va_list va);
+extern void trace_printf(const char *format, ...);
+extern void trace_argv_printf(const char **argv, int count, const char *format, ...);
+
 #endif /* CACHE_H */
diff --git a/exec_cmd.c b/exec_cmd.c
index e30936d72c..5d6a1247b4 100644
--- a/exec_cmd.c
+++ b/exec_cmd.c
@@ -97,26 +97,12 @@ int execv_git_cmd(const char **argv)
 		tmp = argv[0];
 		argv[0] = git_command;
 
-		if (getenv("GIT_TRACE")) {
-			const char **p = argv;
-			fputs("trace: exec:", stderr);
-			while (*p) {
-				fputc(' ', stderr);
-				sq_quote_print(stderr, *p);
-				++p;
-			}
-			putc('\n', stderr);
-			fflush(stderr);
-		}
+		trace_argv_printf(argv, -1, "trace: exec:");
 
 		/* execve() can only ever return if it fails */
 		execve(git_command, (char **)argv, environ);
 
-		if (getenv("GIT_TRACE")) {
-			fprintf(stderr, "trace: exec failed: %s\n",
-				strerror(errno));
-			fflush(stderr);
-		}
+		trace_printf("trace: exec failed: %s\n", strerror(errno));
 
 		argv[0] = tmp;
 	}
diff --git a/git.c b/git.c
index bd07289d71..0c8cfa8d34 100644
--- a/git.c
+++ b/git.c
@@ -179,17 +179,9 @@ static int handle_alias(int *argcp, const char ***argv)
 		if (!strcmp(alias_command, new_argv[0]))
 			die("recursive alias: %s", alias_command);
 
-		if (getenv("GIT_TRACE")) {
-			int i;
-			fprintf(stderr, "trace: alias expansion: %s =>",
-				alias_command);
-			for (i = 0; i < count; ++i) {
-				fputc(' ', stderr);
-				sq_quote_print(stderr, new_argv[i]);
-			}
-			fputc('\n', stderr);
-			fflush(stderr);
-		}
+		trace_argv_printf(new_argv, count,
+				  "trace: alias expansion: %s =>",
+				  alias_command);
 
 		new_argv = xrealloc(new_argv, sizeof(char*) *
 				    (count + *argcp + 1));
@@ -292,16 +284,7 @@ static void handle_internal_command(int argc, const char **argv, char **envp)
 			prefix = setup_git_directory();
 		if (p->option & USE_PAGER)
 			setup_pager();
-		if (getenv("GIT_TRACE")) {
-			int j;
-			fprintf(stderr, "trace: built-in: git");
-			for (j = 0; j < argc; ++j) {
-				fputc(' ', stderr);
-				sq_quote_print(stderr, argv[j]);
-			}
-			putc('\n', stderr);
-			fflush(stderr);
-		}
+		trace_argv_printf(argv, argc, "trace: built-in: git");
 
 		exit(p->fn(argc, argv, prefix));
 	}
diff --git a/imap-send.c b/imap-send.c
index 65c71c602d..6a52dbdca4 100644
--- a/imap-send.c
+++ b/imap-send.c
@@ -110,7 +110,6 @@ static char *next_arg( char ** );
 
 static void free_generic_messages( message_t * );
 
-static int nfvasprintf( char **str, const char *fmt, va_list va );
 static int nfsnprintf( char *buf, int blen, const char *fmt, ... );
 
 
@@ -372,21 +371,6 @@ free_generic_messages( message_t *msgs )
 }
 
 static int
-git_vasprintf( char **strp, const char *fmt, va_list ap )
-{
-	int len;
-	char tmp[1024];
-
-	if ((len = vsnprintf( tmp, sizeof(tmp), fmt, ap )) < 0 || !(*strp = xmalloc( len + 1 )))
-		return -1;
-	if (len >= (int)sizeof(tmp))
-		vsprintf( *strp, fmt, ap );
-	else
-		memcpy( *strp, tmp, len + 1 );
-	return len;
-}
-
-static int
 nfsnprintf( char *buf, int blen, const char *fmt, ... )
 {
 	int ret;
@@ -399,15 +383,6 @@ nfsnprintf( char *buf, int blen, const char *fmt, ... )
 	return ret;
 }
 
-static int
-nfvasprintf( char **str, const char *fmt, va_list va )
-{
-	int ret = git_vasprintf( str, fmt, va );
-	if (ret < 0)
-		die( "Fatal: Out of memory\n");
-	return ret;
-}
-
 static struct {
 	unsigned char i, j, s[256];
 } rs;
diff --git a/quote.c b/quote.c
index e220dcc280..a38786c177 100644
--- a/quote.c
+++ b/quote.c
@@ -74,6 +74,38 @@ char *sq_quote(const char *src)
 	return buf;
 }
 
+char *sq_quote_argv(const char** argv, int count)
+{
+	char *buf, *to;
+	int i;
+	size_t len = 0;
+
+	/* Count argv if needed. */
+	if (count < 0) {
+		for (count = 0; argv[count]; count++)
+			; /* just counting */
+	}
+
+	/* Special case: no argv. */
+	if (!count)
+		return xcalloc(1,1);
+
+	/* Get destination buffer length. */
+	for (i = 0; i < count; i++)
+		len += sq_quote_buf(NULL, 0, argv[i]) + 1;
+
+	/* Alloc destination buffer. */
+	to = buf = xmalloc(len + 1);
+
+	/* Copy into destination buffer. */
+	for (i = 0; i < count; ++i) {
+		*to++ = ' ';
+		to += sq_quote_buf(to, len, argv[i]);
+	}
+
+	return buf;
+}
+
 char *sq_dequote(char *arg)
 {
 	char *dst = arg;
diff --git a/quote.h b/quote.h
index fc5481e78a..a6c4611c25 100644
--- a/quote.h
+++ b/quote.h
@@ -31,6 +31,7 @@
 extern char *sq_quote(const char *src);
 extern void sq_quote_print(FILE *stream, const char *src);
 extern size_t sq_quote_buf(char *dst, size_t n, const char *src);
+extern char *sq_quote_argv(const char** argv, int count);
 
 /* This unwraps what sq_quote() produces in place, but returns
  * NULL if the input does not look like what sq_quote would have
diff --git a/t/test-lib.sh b/t/test-lib.sh
index 470a909891..b0d7990a66 100755
--- a/t/test-lib.sh
+++ b/t/test-lib.sh
@@ -28,7 +28,6 @@ unset GIT_DIR
 unset GIT_EXTERNAL_DIFF
 unset GIT_INDEX_FILE
 unset GIT_OBJECT_DIRECTORY
-unset GIT_TRACE
 unset SHA1_FILE_DIRECTORIES
 unset SHA1_FILE_DIRECTORY
 export GIT_AUTHOR_EMAIL GIT_AUTHOR_NAME
diff --git a/trace.c b/trace.c
new file mode 100644
index 0000000000..90847c3fd8
--- /dev/null
+++ b/trace.c
@@ -0,0 +1,125 @@
+/*
+ * GIT - The information manager from hell
+ *
+ * Copyright (C) 2000-2002 Michael R. Elkins <me@mutt.org>
+ * Copyright (C) 2002-2004 Oswald Buddenhagen <ossi@users.sf.net>
+ * Copyright (C) 2004 Theodore Y. Ts'o <tytso@mit.edu>
+ * Copyright (C) 2006 Mike McCormack
+ * Copyright (C) 2006 Christian Couder
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, write to the Free Software
+ *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+
+#include "cache.h"
+#include "quote.h"
+
+/* Stolen from "imap-send.c". */
+static int git_vasprintf(char **strp, const char *fmt, va_list ap)
+{
+	int len;
+	char tmp[1024];
+
+	if ((len = vsnprintf(tmp, sizeof(tmp), fmt, ap)) < 0 ||
+	    !(*strp = xmalloc(len + 1)))
+		return -1;
+	if (len >= (int)sizeof(tmp))
+		vsprintf(*strp, fmt, ap);
+	else
+		memcpy(*strp, tmp, len + 1);
+	return len;
+}
+
+/* Stolen from "imap-send.c". */
+int nfvasprintf(char **str, const char *fmt, va_list va)
+{
+	int ret = git_vasprintf(str, fmt, va);
+	if (ret < 0)
+		die("Fatal: Out of memory\n");
+	return ret;
+}
+
+/* Get a trace file descriptor from GIT_TRACE env variable. */
+static int get_trace_fd()
+{
+	char *trace = getenv("GIT_TRACE");
+
+	if (!trace || !strcmp(trace, "0") || !strcasecmp(trace," false"))
+		return 0;
+	if (!strcmp(trace, "1") || !strcasecmp(trace, "true"))
+		return STDERR_FILENO;
+	if (strlen(trace) == 1 && isdigit(*trace))
+		return atoi(trace);
+
+	fprintf(stderr, "What does '%s' for GIT_TRACE means ?\n", trace);
+	fprintf(stderr, "Defaulting to tracing on stderr...\n");
+	return STDERR_FILENO;
+}
+
+static const char err_msg[] = "Could not trace into fd given by "
+	"GIT_TRACE environment variable";
+
+void trace_printf(const char *format, ...)
+{
+	char *trace_str;
+	va_list rest;
+	int fd = get_trace_fd();
+
+	if (!fd)
+		return;
+
+	va_start(rest, format);
+	nfvasprintf(&trace_str, format, rest);
+	va_end(rest);
+
+	write_or_whine(fd, trace_str, strlen(trace_str), err_msg);
+
+	free(trace_str);
+}
+
+void trace_argv_printf(const char **argv, int count, const char *format, ...)
+{
+	char *argv_str, *format_str, *trace_str;
+	size_t argv_len, format_len, trace_len;
+	va_list rest;
+	int fd = get_trace_fd();
+
+	if (!fd)
+		return;
+
+	/* Get the argv string. */
+	argv_str = sq_quote_argv(argv, count);
+	argv_len = strlen(argv_str);
+
+	/* Get the formated string. */
+	va_start(rest, format);
+	nfvasprintf(&format_str, format, rest);
+	va_end(rest);
+
+	/* Allocate buffer for trace string. */
+	format_len = strlen(format_str);
+	trace_len = argv_len + format_len + 1; /* + 1 for \n */
+	trace_str = xmalloc(trace_len + 1);
+
+	/* Copy everything into the trace string. */
+	strncpy(trace_str, format_str, format_len);
+	strncpy(trace_str + format_len, argv_str, argv_len);
+	strcpy(trace_str + trace_len - 1, "\n");
+
+	write_or_whine(fd, trace_str, trace_len, err_msg);
+
+	free(argv_str);
+	free(format_str);
+	free(trace_str);
+}
diff --git a/write_or_die.c b/write_or_die.c
index ab4cb8a69c..bfe4eeb649 100644
--- a/write_or_die.c
+++ b/write_or_die.c
@@ -18,3 +18,28 @@ void write_or_die(int fd, const void *buf, size_t count)
 		p += written;
 	}
 }
+
+int write_or_whine(int fd, const void *buf, size_t count, const char *msg)
+{
+	const char *p = buf;
+	ssize_t written;
+
+	while (count > 0) {
+		written = xwrite(fd, p, count);
+		if (written == 0) {
+			fprintf(stderr, "%s: disk full?\n", msg);
+			return 0;
+		}
+		else if (written < 0) {
+			if (errno == EPIPE)
+				exit(0);
+			fprintf(stderr, "%s: write error (%s)\n",
+				msg, strerror(errno));
+			return 0;
+		}
+		count -= written;
+		p += written;
+	}
+
+	return 1;
+}