[PATCH] mingw: help debugging by optionally executing bash with strace

["Johannes Schindelin via GitGitGadget" <gitgitgadget@gmail.com>]

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

MSYS2's strace facility is very useful for debugging... With this patch,
the bash will be executed through strace if the environment variable
GIT_STRACE_COMMANDS is set, which comes in real handy when investigating
issues in the test suite.

Also support passing a path to a log file via GIT_STRACE_COMMANDS to
force Git to call strace.exe with the `-o <path>` argument, i.e. to log
into a file rather than print the log directly.

That comes in handy when the output would otherwise misinterpreted by a
calling process as part of Git's output.

Note: the values "1", "yes" or "true" are *not* specifying paths, but
tell Git to let strace.exe log directly to the console.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
---
    mingw: help debugging by optionally executing bash with MSYS2's strace
    
    This is another patch that has been carried in Git for Windows for some
    five years. Time to graduate.

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-604%2Fdscho%2Fmsys2-strace-v1
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-604/dscho/msys2-strace-v1
Pull-Request: https://github.com/gitgitgadget/git/pull/604

 compat/mingw.c | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/compat/mingw.c b/compat/mingw.c
index d14065d60ec..60c0d36764b 100644
--- a/compat/mingw.c
+++ b/compat/mingw.c
@@ -1479,6 +1479,7 @@ static pid_t mingw_spawnve_fd(const char *cmd, const char **argv, char **deltaen
 	const char *(*quote_arg)(const char *arg) =
 		is_msys2_sh(cmd ? cmd : *argv) ?
 		quote_arg_msys2 : quote_arg_msvc;
+	const char *strace_env;
 
 	/* Make sure to override previous errors, if any */
 	errno = 0;
@@ -1562,6 +1563,31 @@ static pid_t mingw_spawnve_fd(const char *cmd, const char **argv, char **deltaen
 			free(quoted);
 	}
 
+	strace_env = getenv("GIT_STRACE_COMMANDS");
+	if (strace_env) {
+		char *p = path_lookup("strace.exe", 1);
+		if (!p)
+			return error("strace not found!");
+		if (xutftowcs_path(wcmd, p) < 0) {
+			free(p);
+			return -1;
+		}
+		free(p);
+		if (!strcmp("1", strace_env) ||
+		    !strcasecmp("yes", strace_env) ||
+		    !strcasecmp("true", strace_env))
+			strbuf_insert(&args, 0, "strace ", 7);
+		else {
+			const char *quoted = quote_arg(strace_env);
+			struct strbuf buf = STRBUF_INIT;
+			strbuf_addf(&buf, "strace -o %s ", quoted);
+			if (quoted != strace_env)
+				free((char *)quoted);
+			strbuf_insert(&args, 0, buf.buf, buf.len);
+			strbuf_release(&buf);
+		}
+	}
+
 	ALLOC_ARRAY(wargs, st_add(st_mult(2, args.len), 1));
 	xutftowcs(wargs, args.buf, 2 * args.len + 1);
 	strbuf_release(&args);

base-commit: 9fadedd637b312089337d73c3ed8447e9f0aa775
-- 
gitgitgadget