Re: [PATCH 2/2] mingw: replace isatty() hack

Johannes Schindelin [off-list ref] writes:

From: Jeff Hostetler <redacted>

For over a year, Git for Windows has carried a patch that detects the
MSYS2 pseudo ttys used by Git for Windows' default Git Bash (i.e. a
terminal that is not backed by a Win32 Console).

This patch accesses internals that of a previous MSVC runtime that is no
longer valid in newer versions, therefore we needed a replacement for
that hack in order to be able to compile Git using recent Microsoft
Visual C++.

Sorry, but I cannot parse the early part of the first sentence of
the second paragraph before the comma; I am especially having
trouble around the first "that".

This patch back-ports that patch and makes even the MINGW (i.e.
GCC-compiled) Git use it.

As a side effect (which was the reason for the back-port), this patch
also fixes the previous misguided attempt to intercept isatty() so that
it handles character devices (such as /dev/null) as Git expects it.

I had to read the above three times to understand which patches
three instances of "This patch" and one instance of "that patch"
refer to.  I wish it were easier to read, but I think I got them all
right [*1*] after re-reading, and the story made sense to me.

Style: if (fd >= 0 && fd <= 2)

+/* Wrapper for isatty().  Most calls in the main git code

Style: /*
	* multi-line comment block begins with slash-asterisk
        * and ends with asterisk-slash without anything else on
	* the line.
	*/

+ * call isatty(1 or 2) to see if the instance is interactive
+ * and should: be colored, show progress, paginate output.
+ * We lie and give results for what the descriptor WAS at
+ * startup (and ignore any pipe redirection we internally
+ * do).
+ */
+#undef isatty
 int winansi_isatty(int fd)
 {
+	if (fd >=0 && fd <= 2)

Style: if (fd >= 0 && fd <= 2)

+		return fd_is_interactive[fd] != 0;
+	return isatty(fd);
 }

Thanks.


[Footnote]

*1* What I thought I understood in my own words:

    Git for Windows has carried a patch that depended on internals
    of MSVC runtime, but it does not work correctly with recent MSVC
    runtime.  A replacement was written originally for compiling
    with VC++.  The patch in this message is a backport of that
    replacement, and it also fixes the previous attempt to make
    isatty() work.