[PATCH 2/2] Add revision range support on "-" and "@{-1}"

[Kenny Lee Sin Cheong <kenny.lee28@gmail.com>]

Currently it is not be possible to do something like "git checkout
master && git checkout next && git log -.." to see what master has on
top of master.

Allows use of the revision range such as <rev>..- or -..<rev> to see
what HEAD has on top of <rev> or vice versa, respectively.

Also allows use of symmetric differences such as <rev>...- and -...<rev>

This is written on top of Junio's "Just For Fun" patch ($Gmane/265260).

Signed-off-by: Kenny Lee Sin Cheong <kenny.lee28@gmail.com>
---
 revision.c | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/revision.c b/revision.c
index 7778bbd..a79b443 100644
--- a/revision.c
+++ b/revision.c
@@ -1490,6 +1490,7 @@ int handle_revision_arg(const char *arg_, struct rev_info *revs, int flags, unsi
 		int symmetric = *next == '.';
 		unsigned int flags_exclude = flags ^ (UNINTERESTING | BOTTOM);
 		static const char head_by_default[] = "HEAD";
+		static const char prev_rev[] = "@{-1}";
 		unsigned int a_flags;
 
 		*dotdot = 0;
@@ -1499,6 +1500,13 @@ int handle_revision_arg(const char *arg_, struct rev_info *revs, int flags, unsi
 			next = head_by_default;
 		if (dotdot == arg)
 			this = head_by_default;
+		/*  Allows -..<rev> and <rev>..- */
+		if (!strcmp(this, "-")) {
+			this = prev_rev;
+		}
+		if (!strcmp(next, "-")) {
+			next = prev_rev;
+		}
 		if (this == head_by_default && next == head_by_default &&
 		    !symmetric) {
 			/*
@@ -2198,7 +2206,7 @@ int setup_revisions(int argc, const char **argv, struct rev_info *revs, struct s
 	read_from_stdin = 0;
 	for (left = i = 1; i < argc; i++) {
 		const char *arg = argv[i];
-		if (arg[0] == '-' && arg[1]) {
+		if (arg[0] == '-' && !strstr(arg, "..")) {
 			int opts;
 
 			opts = handle_revision_pseudo_opt(submodule,
@@ -2220,6 +2228,7 @@ int setup_revisions(int argc, const char **argv, struct rev_info *revs, struct s
 				continue;
 			}
 
+
 			opts = handle_revision_opt(revs, argc - i, argv + i, &left, argv);
 			if (opts > 0) {
 				i += opts - 1;
@@ -2229,7 +2238,10 @@ int setup_revisions(int argc, const char **argv, struct rev_info *revs, struct s
 				exit(128);
 			continue;
 		}
-
+		if (strstr(arg, "..")) {
+			handle_revision_arg(arg, revs, flags, revarg_opt);
+			continue;
+		}
 
 		if (handle_revision_arg(arg, revs, flags, revarg_opt)) {
 			int j;
-- 
2.3.2.225.gebdc58a