archive: replace write_or_die() calls with write_block_or_die()

MinGit for Windows comes without `gzip` bundled inside,
git-archive uses `gzip -cn` to compress tar files but
for this to work, gzip needs to be present on the host
system, which sometimes is not the case

In the next commit, we will change the gzip compression
so that we no longer spawn `gzip` but let zlib perform
the compression in the same process

In preparation for this, we consolidate all the block
writes into a single function

Closes: #1970
Signed-off-by: Rohit Ashiwal <[email protected]>

Author: r1walz

archive-tar.c

@@ -17,6 +17,8 @@ static unsigned long offset;
 
 static int tar_umask = 002;
 
+static gzFile gzip;
+
 static int write_tar_filter_archive(const struct archiver *ar,
 				    struct archiver_args *args);
 
@@ -38,11 +40,21 @@ static int write_tar_filter_archive(const struct archiver *ar,
 #define USTAR_MAX_MTIME 077777777777ULL
 #endif
 
+/* writes out the whole block, or dies if fails */
+static void write_block_or_die(const char *block) {
+	if (gzip) {
+		if (gzwrite(gzip, block, (unsigned) BLOCKSIZE) != BLOCKSIZE)
+			die(_("gzwrite failed"));
+	} else {
+		write_or_die(1, block, BLOCKSIZE);
+	}
+}
+
 /* writes out the whole block, but only if it is full */
 static void write_if_needed(void)
 {
 	if (offset == BLOCKSIZE) {
-		write_or_die(1, block, BLOCKSIZE);
+		write_block_or_die(block);
 		offset = 0;
 	}
 }
@@ -66,7 +78,7 @@ static void do_write_blocked(const void *data, unsigned long size)
 		write_if_needed();
 	}
 	while (size >= BLOCKSIZE) {
-		write_or_die(1, buf, BLOCKSIZE);
+		write_block_or_die(buf);
 		size -= BLOCKSIZE;
 		buf += BLOCKSIZE;
 	}
@@ -101,10 +113,10 @@ static void write_trailer(void)
 {
 	int tail = BLOCKSIZE - offset;
 	memset(block + offset, 0, tail);
-	write_or_die(1, block, BLOCKSIZE);
+	write_block_or_die(block);
 	if (tail < 2 * RECORDSIZE) {
 		memset(block, 0, offset);
-		write_or_die(1, block, BLOCKSIZE);
+		write_block_or_die(block);
 	}
 }