Introduce trivial new pager.c helper infrastructure

This introduces the new function

	void setup_pager(void);

to set up output to be written through a pager applocation.

All in preparation for doing the simple scripts in C.

Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>

diff --git a/Makefile b/Makefile
index 35754895dfcd962f0ae10ed6182f48bc3d9adfe3..0b1a9988b45944ece4769e4ac5de47e51dad69c5 100644 (file)
--- a/Makefile
+++ b/Makefile
@@ -205,7 +205,7 @@ LIB_OBJS = \
        quote.o read-cache.o refs.o run-command.o \
        server-info.o setup.o sha1_file.o sha1_name.o strbuf.o \
        tag.o tree.o usage.o config.o environment.o ctype.o copy.o \
-       fetch-clone.o revision.o \
+       fetch-clone.o revision.o pager.o \
        $(DIFF_OBJS)
 
 LIBS = $(LIB_FILE)

diff --git a/cache.h b/cache.h
index 58eec00e0ed1d2c20c51d3973d7463ccef0afb26..3af6b868e86032af59ce31c3cbe714b7e5a0ee25 100644 (file)
--- a/cache.h
+++ b/cache.h
@@ -352,4 +352,7 @@ extern int copy_fd(int ifd, int ofd);
 extern int receive_unpack_pack(int fd[2], const char *me, int quiet);
 extern int receive_keep_pack(int fd[2], const char *me, int quiet);
 
+/* pager.c */
+extern void setup_pager(void);
+
 #endif /* CACHE_H */

diff --git a/pager.c b/pager.c
new file mode 100644 (file)
index 0000000..1364e15
--- /dev/null
+++ b/pager.c
@@ -0,0 +1,48 @@
+#include "cache.h"
+
+/*
+ * This is split up from the rest of git so that we might do
+ * something different on Windows, for example.
+ */
+
+static void run_pager(void)
+{
+       const char *prog = getenv("PAGER");
+       if (!prog)
+               prog = "less";
+       setenv("LESS", "-S", 0);
+       execlp(prog, prog, NULL);
+}
+
+void setup_pager(void)
+{
+       pid_t pid;
+       int fd[2];
+
+       if (!isatty(1))
+               return;
+       if (pipe(fd) < 0)
+               return;
+       pid = fork();
+       if (pid < 0) {
+               close(fd[0]);
+               close(fd[1]);
+               return;
+       }
+
+       /* return in the child */
+       if (!pid) {
+               dup2(fd[1], 1);
+               close(fd[0]);
+               close(fd[1]);
+               return;
+       }
+
+       /* The original process turns into the PAGER */
+       dup2(fd[0], 0);
+       close(fd[0]);
+       close(fd[1]);
+
+       run_pager();
+       exit(255);
+}