rc tools git: blame-jump to handle buffer modifications since blame

If I run

    git blame
    execute-keys 10o<esc>,j
    git blame-jump

that'll jump to the wrong commit.

Use a flag-lines option to tell if a line still has blame information
cached.

Closes #5084

rc/tools/git.kak

@@ -74,6 +74,7 @@ hook -group git-show-branch-highlight global WinSetOption filetype=git-show-bran
 }
 
 declare-option -hidden line-specs git_blame_flags
+declare-option -hidden line-specs git_blame_index
 declare-option -hidden str git_blame
 declare-option -hidden str git_blob
 declare-option -hidden line-specs git_diff_flags
@@ -180,6 +181,7 @@ define-command -params 1.. \
     hide_blame() {
         printf %s "
             set-option buffer git_blame_flags $kak_timestamp
+            set-option buffer git_blame_index $kak_timestamp
             set-option buffer git_blame %{}
             remove-highlighter window/git-blame
             unmap window normal <ret> %{:git blame-jump<ret>}
@@ -272,6 +274,7 @@ define-command -params 1.. \
             cd_bufdir
             printf %s "evaluate-commands -client '$kak_client' %{
                       set-option buffer=$kak_bufname git_blame_flags '$kak_timestamp'
+                      set-option buffer=$kak_bufname git_blame_index '$kak_timestamp'
                       set-option buffer=$kak_bufname git_blame ''
                   }" | kak -p ${kak_session}
             git blame --incremental "$@" <${contents_fifo} | perl -wne '
@@ -297,9 +300,11 @@ define-command -params 1.. \
                       }
                       open CMD, "|-", "kak -p $ENV{kak_session}";
                       print CMD "set-option -add buffer=$ENV{kak_bufname} git_blame_flags $flags;";
+                      print CMD "set-option -add buffer=$ENV{kak_bufname} git_blame_index $index;";
                       print CMD "set-option -add buffer=$ENV{kak_bufname} git_blame " . quote $raw_blame;
                       close(CMD);
                       $flags = "";
+                      $index = "";
                       $raw_blame = "";
                       $last_sent = $now;
                   }
@@ -310,6 +315,9 @@ define-command -params 1.. \
                       $sha = $1;
                       $line = $3;
                       $count = $4;
+                      for ( my $i = 0; $i < $count; $i++ ) {
+                          $index .= " " . ($line+$i) . "|$.,$i";
+                      }
                   }
                   if (m/^author /) {
                       $authors{$sha} = substr($_,7);
@@ -483,11 +491,16 @@ define-command -params 1.. \
     blame_jump() {
         echo >${kak_command_fifo} "echo -to-file ${kak_response_fifo} -- %opt{git_blame}"
         blame_info=$(cat < ${kak_response_fifo})
+        blame_index=
         cursor_column=${kak_cursor_column}
         cursor_line=${kak_cursor_line}
-        if [ -z "$blame_info" ] && {
+        if [ -n "$blame_info" ]; then {
-            [ "${kak_opt_filetype}" = git-diff ] || [ "${kak_opt_filetype}" = git-log ]
+            echo >${kak_command_fifo} "
-        }; then {
+                update-option buffer git_blame_index
+                echo -to-file ${kak_response_fifo} -- %opt{git_blame_index}
+            "
+            blame_index=$(cat < ${kak_response_fifo})
+        } elif [ "${kak_opt_filetype}" = git-diff ] || [ "${kak_opt_filetype}" = git-log ]; then {
             printf >${kak_command_fifo} %s '
                 evaluate-commands -draft %{
                     try %{
@@ -528,7 +541,7 @@ define-command -params 1.. \
             cursor_line=$3
             cursor_column=$4
             blame_info=$(git blame --porcelain "$starting_commit" -L"$cursor_line,$cursor_line" -- "$file")
-        } elif [ -z "$blame_info" ]; then {
+        } else {
             set --
             eval "$prepare_git_blame_args"
             blame_info=$(git blame --porcelain -L"$cursor_line,$cursor_line" "$@" <${contents_fifo})
@@ -536,7 +549,7 @@ define-command -params 1.. \
                 rm -r $(dirname $contents_fifo)
             fi
         } fi
-        eval "$(printf %s "$blame_info" |
+        eval "$(printf '%s\n---\n%s' "$blame_index" "$blame_info" |
                 client=${kak_opt_docsclient:-$kak_client} \
                 cursor_line=$cursor_line cursor_column=$cursor_column \
                 perl -wne '
@@ -562,8 +575,28 @@ define-command -params 1.. \
                     return "$SQ$token$SQ";
                 }
                 $target = $ENV{"cursor_line"};
+                $state = "index";
             }
             chomp;
+            if ($state eq "index") {
+                if ($_ eq "---") {
+                    $state = "blame";
+                    next;
+                }
+                @blame_index = split;
+                next unless @blame_index;
+                shift @blame_index;
+                foreach (@blame_index) {
+                    $_ =~ m{(\d+)\|(\d+),(\d+)} or die "bad blame index flag: $_";
+                    my $buffer_line = $1;
+                    if ($buffer_line == $target) {
+                        $target_in_blame = $2;
+                        $target_offset = $3;
+                        last;
+                    }
+                }
+                defined $target_in_blame and next, or last;
+            }
             if (m/^([0-9a-f]+) ([0-9]+) ([0-9]+) ([0-9]+)/) {
                 if ($done) {
                     last;
@@ -572,16 +605,27 @@ define-command -params 1.. \
                 $old_line = $2;
                 $new_line = $3;
                 $count = $4;
+                if (defined $target_in_blame) {
+                    if ($target_in_blame == $. - 2) {
+                        $old_line += $target_offset;
+                        $done = 1;
+                    }
+                } else {
                     if ($new_line <= $target and $target < $new_line + $count) {
                         $old_line += $target - $new_line;
                         $done = 1;
                     }
                 }
+            }
             if (m/^filename /) { $old_filenames{$sha} = substr($_,9) }
             if (m/^author /) { $authors{$sha} = substr($_,7) }
             if (m/^author-time ([0-9]*)/) { $dates{$sha} = strftime("%F", localtime $1) }
             if (m/^summary /) { $summaries{$sha} = substr($_,8) }
             END {
+                if (@blame_index and not defined $target_in_blame) {
+                    print "echo fail git blame-jump: line has no blame information;";
+                    exit;
+                }
                 if (not defined $sha) {
                     print "echo fail git blame-jump: missing blame info";
                     exit;