From a2cebdb88437086d5083c893e472275e1cdf1957 Mon Sep 17 00:00:00 2001
From: Jonas Fonseca <fonseca@diku.dk>
Date: Thu, 15 Jan 2009 22:41:58 +0100
Subject: [PATCH] Add support for loading blame for parent commits

Requested by Jeff King in <20080410040213.GA29618@sigill.intra.peff.net>
---
 NEWS       |  2 ++
 TODO       |  3 ---
 manual.txt |  3 ++-
 tig.c      | 60 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 64 insertions(+), 4 deletions(-)

diff --git a/NEWS b/NEWS
index 6109737..d8e1468 100644
--- a/NEWS
+++ b/NEWS
@@ -17,6 +17,8 @@ Improvements:
  - Tree view: annotate entries with commit information.
  - Tree & blob view: open any blob in an editor.
  - Stage & main view: restore view position when reloading.
+ - Blame view: load blame for parent commit. For merge commits the parent
+   is queried. Bound to ',' by default via the existing "parent" action.
 
 Bug fixes:
 
diff --git a/TODO b/TODO
index 082c637..1b88728 100644
--- a/TODO
+++ b/TODO
@@ -28,6 +28,3 @@ Features that should be explored.
 
  - Blame view: Allow names in the author column to be abbreviated to
    initials. Will optimize screen usage for the blame view.
-
- - Blame view: make it possible to jump/load blame for parents. Idea by
-   Jeff King.
diff --git a/manual.txt b/manual.txt
index 87f9492..fe4d311 100644
--- a/manual.txt
+++ b/manual.txt
@@ -345,7 +345,8 @@ Up	This key is "context sensitive" and will move the cursor one \
 	to display it.
 Down	Similar to 'Up' but will move down.
 ','	Move to parent. In the tree view, this means switch to the parent \
-	directory.
+	directory. In the blame view it will load blame for the parent \
+	commit. For merges the parent is queried.
 -----------------------------------------------------------------------------
 
 [[cursor-nav]]
diff --git a/tig.c b/tig.c
index 7997091..095e9c6 100644
--- a/tig.c
+++ b/tig.c
@@ -3337,6 +3337,60 @@ parse_author_line(char *ident, char *author, size_t authorsize, struct tm *tm)
 	}
 }
 
+static enum input_status
+select_commit_parent_handler(void *data, char *buf, int c)
+{
+	size_t parents = *(size_t *) data;
+	int parent = 0;
+
+	if (!isdigit(c))
+		return INPUT_SKIP;
+
+	if (*buf)
+		parent = atoi(buf) * 10;
+	parent += c - '0';
+
+	if (parent > parents)
+		return INPUT_SKIP;
+	return INPUT_OK;
+}
+
+static bool
+select_commit_parent(const char *id, char rev[SIZEOF_REV])
+{
+	char buf[SIZEOF_STR * 4];
+	const char *revlist_argv[] = {
+		"git", "rev-list", "-1", "--parents", id, NULL
+	};
+	int parents;
+
+	if (!run_io_buf(revlist_argv, buf, sizeof(buf)) ||
+	    !*chomp_string(buf) ||
+	    (parents = (strlen(buf) / 40) - 1) < 0) {
+		report("Failed to get parent information");
+		return FALSE;
+
+	} else if (parents == 0) {
+		report("The selected commit has no parents");
+		return FALSE;
+	}
+
+	if (parents > 1) {
+		char prompt[SIZEOF_STR];
+		char *result;
+
+		if (!string_format(prompt, "Which parent? [1..%d] ", parents))
+			return FALSE;
+		result = prompt_input(prompt, select_commit_parent_handler, &parents);
+		if (!result)
+			return FALSE;
+		parents = atoi(result);
+	}
+
+	string_copy_rev(rev, &buf[41 * parents]);
+	return TRUE;
+}
+
 /*
  * Pager backend
  */
@@ -4365,6 +4419,12 @@ blame_request(struct view *view, enum request request, struct line *line)
 		}
 		break;
 
+	case REQ_PARENT:
+		if (check_blame_commit(blame) &&
+		    select_commit_parent(blame->commit->id, opt_ref))
+			open_view(view, REQ_VIEW_BLAME, OPEN_REFRESH);
+		break;
+
 	case REQ_ENTER:
 		if (!blame->commit) {
 			report("No commit loaded yet");
-- 
2.32.0.93.g670b81a890