[PATCH v4 2/7] trace: avoid unnecessary quoting

[Nguyễn Thái Ngọc Duy]

From: Jeff King <p...@peff.net>

Trace output which contains arbitrary strings (e.g., the
arguments to commands which we are running) is always passed
through sq_quote_buf(). That function always adds
single-quotes, even if the output consists of vanilla
characters. This can make the output a bit hard to read.

Let's avoid the quoting if there are no characters which a
shell would interpret. Trace output doesn't necessarily need
to be shell-compatible, but:

  - the shell language is a good ballpark for what humans
    consider readable (well, humans versed in command line
    tools)

  - the run_command bits can be cut-and-pasted to a shell,
    and we'll keep that property

  - it covers any cases which would make the output
    visually ambiguous (e.g., embedded whitespace or quotes)

Signed-off-by: Jeff King <p...@peff.net>
Signed-off-by: Nguyễn Thái Ngọc Duy <pclo...@gmail.com>
---
 quote.c | 26 ++++++++++++++++++++++++++
 quote.h |  8 ++++++++
 trace.c |  4 ++--
 3 files changed, 36 insertions(+), 2 deletions(-)

diff --git a/quote.c b/quote.c
index b2970da627..37d2686865 100644
--- a/quote.c
+++ b/quote.c
@@ -43,6 +43,22 @@ void sq_quote_buf(struct strbuf *dst, const char *src)
        free(to_free);
 }
 
+void sq_quote_buf_pretty(struct strbuf *dst, const char *src)
+{
+       static const char ok_punct[] = "+,-./:=@_^";
+       const char *p;
+
+       for (p = src; *p; p++) {
+               if (!isalpha(*p) && !isdigit(*p) && !strchr(ok_punct, *p)) {
+                       sq_quote_buf(dst, src);
+                       return;
+               }
+       }
+
+       /* if we get here, we did not need quoting */
+       strbuf_addstr(dst, src);
+}
+
 void sq_quotef(struct strbuf *dst, const char *fmt, ...)
 {
        struct strbuf src = STRBUF_INIT;
@@ -68,6 +84,16 @@ void sq_quote_argv(struct strbuf *dst, const char **argv)
        }
 }
 
+void sq_quote_argv_pretty(struct strbuf *dst, const char **argv)
+{
+       int i;
+
+       for (i = 0; argv[i]; i++) {
+               strbuf_addch(dst, ' ');
+               sq_quote_buf_pretty(dst, argv[i]);
+       }
+}
+
 static char *sq_dequote_step(char *arg, char **next)
 {
        char *dst = arg;
diff --git a/quote.h b/quote.h
index 48a75a416b..ea992dcc91 100644
--- a/quote.h
+++ b/quote.h
@@ -33,6 +33,14 @@ extern void sq_quote_buf(struct strbuf *, const char *src);
 extern void sq_quote_argv(struct strbuf *, const char **argv);
 extern void sq_quotef(struct strbuf *, const char *fmt, ...);
 
+/*
+ * These match their non-pretty variants, except that they avoid
+ * quoting when there are no exotic characters. These should only be used for
+ * human-readable output, as sq_dequote() is not smart enough to dequote it.
+ */
+void sq_quote_buf_pretty(struct strbuf *, const char *src);
+void sq_quote_argv_pretty(struct strbuf *, const char **argv);
+
 /* This unwraps what sq_quote() produces in place, but returns
  * NULL if the input does not look like what sq_quote would have
  * produced.
diff --git a/trace.c b/trace.c
index fa9174fc4b..9784915be1 100644
--- a/trace.c
+++ b/trace.c
@@ -157,7 +157,7 @@ static void trace_argv_vprintf_fl(const char *file, int 
line,
 
        strbuf_vaddf(&buf, format, ap);
 
-       sq_quote_argv(&buf, argv);
+       sq_quote_argv_pretty(&buf, argv);
        print_trace_line(&trace_default_key, &buf);
 }
 
@@ -426,6 +426,6 @@ void trace_command_performance(const char **argv)
                atexit(print_command_performance_atexit);
 
        strbuf_reset(&command_line);
-       sq_quote_argv(&command_line, argv);
+       sq_quote_argv_pretty(&command_line, argv);
        command_start_time = getnanotime();
 }
-- 
2.15.1.600.g899a5f85c6