[PATCH v3] write-or-die: make GIT_FLUSH a Boolean environment variable

From: Chandra Pratap <chandrapratap3519@gmail.com>

Among Git's environment variable, the ones marked as "Boolean" accept values in a way similar to Boolean configuration variables, i.e. values like 'yes', 'on', 'true' and positive numbers are taken as "on" and values like 'no', 'off', 'false' are taken as "off". GIT_FLUSH can be used to force Git to use non-buffered I/O when writing to stdout. It can only accept two values, '1' which causes Git to flush more often and '0' which makes all output buffered. Make GIT_FLUSH accept more values besides '0' and '1' by turning it into a Boolean environment variable, modifying the required logic. Update the related documentation.

Signed-off-by: Chandra Pratap <chandrapratap3519@gmail.com>
---
    write-or-die: make GIT_FLUSH a Boolean environment variable

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-1628%2FChand-ra%2Fgit_flush-v3
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-1628/Chand-ra/git_flush-v3
Pull-Request: https://github.com/gitgitgadget/git/pull/1628

Range-diff vs v2:

 1:  585c76fff68 ! 1:  c98885c0ede write-or-die: make GIT_FLUSH a Boolean environment variable
     @@ Documentation/git.txt: for further details.
      -	If this environment variable is set to "1", then commands such
      +	If this Boolean environment variable is set to true, then commands such
       	as 'git blame' (in incremental mode), 'git rev-list', 'git log',
     --	'git check-attr' and 'git check-ignore' will
     --	force a flush of the output stream after each record have been
     --	flushed. If this
     + 	'git check-attr' and 'git check-ignore' will
     + 	force a flush of the output stream after each record have been
     + 	flushed. If this
      -	variable is set to "0", the output of these commands will be done
     --	using completely buffered I/O.   If this environment variable is
     --	not set, Git will choose buffered or record-oriented flushing
     --	based on whether stdout appears to be redirected to a file or not.
     -+	'git check-attr' and 'git check-ignore' will force a flush of the output
     -+	stream after each record have been flushed. If this variable is set to
     -+	false, the output of these commands will be done using completely buffered
     -+	I/O. If this environment variable is not set, Git will choose buffered or
     -+	record-oriented flushing based on whether stdout appears to be redirected
     -+	to a file or not.
     - 
     - `GIT_TRACE`::
     - 	Enables general trace messages, e.g. alias expansion, built-in
     ++	variable is set to false, the output of these commands will be done
     + 	using completely buffered I/O.   If this environment variable is
     + 	not set, Git will choose buffered or record-oriented flushing
     + 	based on whether stdout appears to be redirected to a file or not.
      
       ## write-or-die.c ##
     -@@ write-or-die.c: void maybe_flush_or_die(FILE *f, const char *desc)
     +@@
     + void maybe_flush_or_die(FILE *f, const char *desc)
       {
       	static int skip_stdout_flush = -1;
     - 	struct stat st;
     +-	struct stat st;
      -	char *cp;
       
       	if (f == stdout) {
     @@ write-or-die.c: void maybe_flush_or_die(FILE *f, const char *desc)
      -			if (cp)
      -				skip_stdout_flush = (atoi(cp) == 0);
      -			else if ((fstat(fileno(stdout), &st) == 0) &&
     -+			if (!git_env_bool("GIT_FLUSH", -1))
     -+				skip_stdout_flush = 1;
     -+			else if (!fstat(fileno(stdout), &st) &&
     - 				 S_ISREG(st.st_mode))
     - 				skip_stdout_flush = 1;
     - 			else
     +-				 S_ISREG(st.st_mode))
     +-				skip_stdout_flush = 1;
     +-			else
     +-				skip_stdout_flush = 0;
     ++			skip_stdout_flush = git_env_bool("GIT_FLUSH", -1);
     ++			if (skip_stdout_flush < 0) {
     ++				struct stat st;
     ++				if (fstat(fileno(stdout), &st))
     ++					skip_stdout_flush = 0;
     ++				else
     ++					skip_stdout_flush = S_ISREG(st.st_mode);
     ++			}
     + 		}
     + 		if (skip_stdout_flush && !ferror(f))
     + 			return;

 Documentation/git.txt |  5 ++---
 write-or-die.c        | 19 ++++++++-----------
 2 files changed, 10 insertions(+), 14 deletions(-)