rc tools git: command for easy recursive blaming

Our ":git blame" annotates each line with the most recent commit.
However often a line has been modified by several commits.

Introduce ":git blame-jump" which shows the commit that added the
line at cursor. Crucially, it works also in Git diff buffers, so it
can be used recursively to find the full history of a line.

To do the recursive blame from a diff, I need to navigate to the
old (deleted) version of a line. Since old and new line are usually
neighbors. Speed up the common scenario of finding the old version
by making ":git blame-jump" jump to the new version. This means the
initial diff view might not include the commit message etc. Compensate
this by showing the commit's date+author+subject in the status line.

Here are some test cases.
- run blame-jump after "git blame"
- create an uncommitted or unsaved line, run "git blame" and
  "blame-jump" on the uncommitted line
- run blame-jump without running "git blame"
- run blame-jump in "git show"
- run blame-jump in "git diff HEAD"
- run blame-jump in "git diff --cached"
- run blame-jump in "git diff" (YMMV if there are cached changes,
  could fix that)

Naming: there are some similar commands in the wild [1];
they are usually called "show-blamed" or similar, but they
don't jump to the corresponding line.  Also our list of git
commands is getting a bit messy (especially the undocumented
show-diff/hide-diff/next-hunk/prev-hunk; subject first naming seems
better).

[1]: f6e78ec4c0/kakrc (L423)

Future work: to go back to the previously-blamed commit we need to
have had the foresight to use "rename-buffer". Perhaps we want to
add some kind of buffer stack (like Magit does for example).

rc/filetype/diff-parse.pl

@@ -39,11 +39,17 @@ while (defined $ARGV[0]) {
 # Inputs
 our $directory = $ENV{PWD};
 our $strip;
+our $in_file;
+our $in_file_line;
 our $version = "+";
 
 eval $begin if defined $begin;
 
+$in_file = "$directory/$in_file" if defined $in_file;
+
 # Outputs
+our $diff_line = 0;
+our $commit;
 our $file;
 our $file_line;
 our $diff_line_text;
@@ -83,8 +89,13 @@ sub strip {
 }
 
 while (<STDIN>) {
+    $diff_line++;
     s/^(> )*//g;
     $diff_line_text = $_;
+    if (m{^commit (\w+)}) {
+        $commit = $1;
+        next;
+    }
     if (m{^diff\b}) {
         $state = "header";
         $is_recursive_diff = 1;
@@ -116,6 +127,11 @@ while (<STDIN>) {
            $other_file_line++ if defined $other_file_line;
         }
     }
+    if (defined $in_file and defined $file and $file eq $in_file) {
+        if (defined $in_file_line and defined $file_line and $file_line >= $in_file_line) {
+            last;
+        }
+    }
 }
 if (not defined $file) {
     $file = ($fallback_file or $other_file);

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 str git_blame
 declare-option -hidden line-specs git_diff_flags
 declare-option -hidden int-list git_hunk_list
 
@@ -83,8 +84,9 @@ define-command -params 1.. \
         All the optional arguments are forwarded to the git utility
         Available commands:
             add
-            apply (alias for "patch git apply")
+            apply      - alias for "patch git apply"
-            blame (toggle blame annotations)
+            blame      - toggle blame annotations
+            blame-jump - show the commit that added the line at cursor
             checkout
             commit
             diff
@@ -107,6 +109,7 @@ define-command -params 1.. \
         printf %s\\n \
             apply \
             blame \
+            blame-jump \
             checkout \
             commit \
             diff \
@@ -142,6 +145,9 @@ define-command -params 1.. \
             exit 1
         }
     }
+    kakquote() {
+        printf "%s" "$1" | sed "s/'/''/g; 1s/^/'/; \$s/\$/'/"
+    }
 
     show_git_cmd_output() {
         local filetype
@@ -158,21 +164,38 @@ define-command -params 1.. \
         mkfifo ${output}
         ( git "$@" > ${output} 2>&1 & ) > /dev/null 2>&1 < /dev/null
 
-        printf %s "evaluate-commands -try-client '$kak_opt_docsclient' %{
+        printf %s "evaluate-commands -try-client '$kak_opt_docsclient' '
                   edit! -fifo ${output} *git*
-                  set-option buffer filetype '${filetype}'
+                  set-option buffer filetype ${filetype}
-                  hook -always -once buffer BufCloseFifo .* %{ nop %sh{ rm -r $(dirname ${output}) } }
+                  hook -always -once buffer BufCloseFifo .* ''
-              }"
+                      nop %sh{ rm -r $(dirname ${output}) }
+                      $(printf %s "${on_close_fifo}" | sed "s/'/''''/g")
+                  ''
+        '"
     }
 
     hide_blame() {
         printf %s "
             set-option buffer=$kak_bufname git_blame_flags $kak_timestamp
+            set-option buffer=$kak_bufname git_blame ''
             remove-highlighter window/git-blame
         "
     }
 
-    run_git_blame() {
+    prepare_git_blame_args='
+        contents_fifo=$(mktemp -d "${TMPDIR:-/tmp}"/kak-git.XXXXXXXX)/fifo
+        mkfifo ${contents_fifo}
+        echo >${kak_command_fifo} "evaluate-commands -save-regs | %{
+            set-register | %{
+                contents=\$(cat; printf .)
+                ( printf %s \"\${contents%.}\" >${contents_fifo} ) >/dev/null 2>&1 &
+            }
+            execute-keys -client ${kak_client} -draft %{%<a-|><ret>}
+        }"
+        set -- "$@" --contents - -- "${kak_buffile}"
+    '
+
+    blame_toggle() {
         echo >${kak_command_fifo} "try %{
             add-highlighter window/git-blame flag-lines Information git_blame_flags
             echo -to-file ${kak_response_fifo}
@@ -180,22 +203,21 @@ define-command -params 1.. \
             echo -to-file ${kak_response_fifo} 'hide_blame; exit'
         }"
         eval $(cat ${kak_response_fifo})
-        contents_fifo=$(mktemp -d "${TMPDIR:-/tmp}"/kak-git.XXXXXXXX)/fifo
+        eval "$prepare_git_blame_args"
-        mkfifo ${contents_fifo}
-        echo >${kak_command_fifo} 'evaluate-commands -save-regs | %{
-            set-register | %{
-                contents=$(cat; printf .)
-                ( printf %s "${contents%.}" >'${contents_fifo}' ) >/dev/null 2>&1 &
-            }
-            execute-keys -client '${kak_client}' -draft %{%<a-|><ret>}
-        }'
         (
             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 ''
                   }" | kak -p ${kak_session}
-            git blame "$@" --incremental "${kak_buffile}" --contents - <$contents_fifo | perl -wne '
+            git blame --incremental "$@" <${contents_fifo} | perl -wne '
                   use POSIX qw(strftime);
+                  sub quote {
+                      my $SQ = "'\''";
+                      my $token = shift;
+                      $token =~ s/$SQ/$SQ$SQ/g;
+                      return "$SQ$token$SQ";
+                  }
                   sub send_flags {
                       my $flush = shift;
                       if (not defined $line) { return; }
@@ -210,11 +232,14 @@ define-command -params 1.. \
                           return
                       }
                       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_flags $flags;";
+                      print CMD "set-option -add buffer=$ENV{kak_bufname} git_blame " . quote $raw_blame;
                       close(CMD);
                       $flags = "";
+                      $raw_blame = "";
                       $last_sent = $now;
                   }
+                  $raw_blame .= $_;
                   chomp;
                   if (m/^([0-9a-f]+) ([0-9]+) ([0-9]+) ([0-9]+)/) {
                       send_flags(0);
@@ -389,6 +414,152 @@ define-command -params 1.. \
               } }"
     }
 
+    blame_jump() {
+        echo >${kak_command_fifo} "echo -to-file ${kak_response_fifo} -- %opt{git_blame}"
+        blame_info=$(cat < ${kak_response_fifo})
+        cursor_column=${kak_cursor_column}
+        cursor_line=${kak_cursor_line}
+        if [ -z "$blame_info" ] && {
+            [ "${kak_opt_filetype}" = git-diff ] || [ "${kak_opt_filetype}" = git-log ]
+        }; then {
+            printf >${kak_command_fifo} %s '
+                evaluate-commands -draft %{
+                    try %{
+                        execute-keys <a-l><semicolon><a-?>^commit<ret><a-semicolon>
+                    } catch %{
+                        # Missing commit line, assume it is an uncommitted change.
+                        execute-keys <a-l><semicolon><a-?>\A<ret><a-semicolon>
+                    }
+                    require-module diff
+                    try %{
+                        diff-parse BEGIN %{
+                            $version = "-";
+                        } END %{
+                            if ($diff_line_text !~ m{^[ -]}) {
+                                print "set-register e fail git blame-jump: recursive blame only works on context or deleted lines";
+                            } else {
+                                if (not defined $commit) {
+                                    $commit = "HEAD";
+                                } else {
+                                    $commit = "$commit~" if $diff_line_text =~ m{^[- ]};
+                                }
+                                printf "echo -to-file '${kak_response_fifo}' -quoting shell %s %s %d %d",
+                                        $commit, quote($file), $file_line, ('$cursor_column' - 1);
+                            }
+                        }
+                    } catch %{
+                        echo -to-file '${kak_response_fifo}' -quoting shell -- %val{error}
+                    }
+                }
+            '
+            eval set -- "$(cat ${kak_response_fifo})"
+            if [ $# -eq 1 ]; then
+                echo fail -- "$(kakquote "$1")"
+                exit
+            fi
+            starting_commit=$1
+            file=$2
+            cursor_line=$3
+            cursor_column=$4
+            blame_info=$(git blame --porcelain "$starting_commit" -L"$cursor_line,$cursor_line" -- "$file")
+        } elif [ -z "$blame_info" ]; then {
+            set --
+            eval "$prepare_git_blame_args"
+            blame_info=$(git blame --porcelain -L"$cursor_line,$cursor_line" "$@" <${contents_fifo})
+            rm -r $(dirname $contents_fifo)
+        } fi
+        eval "$(printf %s "$blame_info" |
+                client=${kak_opt_docsclient:-$kak_client} \
+                cursor_line=$cursor_line cursor_column=$cursor_column \
+                perl -wne '
+            BEGIN {
+                use POSIX qw(strftime);
+                our $SQ = "'\''";
+                sub escape {
+                   return shift =~ s/$SQ/$SQ$SQ/gr
+                }
+                sub quote {
+                    my $token = escape shift;
+                    return "$SQ$token$SQ";
+                }
+                sub shellquote {
+                    my $token = shift;
+                    $token =~ s/$SQ/$SQ\\$SQ$SQ/g;
+                    return "$SQ$token$SQ";
+                }
+                sub perlquote {
+                    my $token = shift;
+                    $token =~ s/\\/\\\\/g;
+                    $token =~ s/$SQ/\\$SQ/g;
+                    return "$SQ$token$SQ";
+                }
+                $target = $ENV{"cursor_line"};
+            }
+            chomp;
+            if (m/^([0-9a-f]+) ([0-9]+) ([0-9]+) ([0-9]+)/) {
+                if ($done) {
+                    last;
+                }
+                $sha = $1;
+                $old_line = $2;
+                $new_line = $3;
+                $count = $4;
+                if ($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 (not defined $sha) {
+                    print "echo fail git blame-jump: missing blame info";
+                    exit;
+                }
+                if (not $done) {
+                    print "echo \"fail git blame-jump: line not found in annotations (blame still loading?)\"";
+                    exit;
+                }
+                $info = "{Information}{\\}";
+                if ($sha =~ m{^0+$}) {
+                    $old_filename = $ENV{"kak_buffile"};
+                    $old_filename = substr $old_filename, length($ENV{"PWD"}) + 1;
+                    $show_diff = "diff HEAD";
+                    $info .= "Not committed yet";
+                } else {
+                    $old_filename = $old_filenames{$sha};
+                    $author = $authors{$sha};
+                    $date = $dates{$sha};
+                    $summary = $summaries{$sha};
+                    $show_diff = "show $sha";
+                    $info .= "$date $author \"$summary\"";
+                }
+                $on_close_fifo = "
+                    evaluate-commands -draft $SQ
+                        execute-keys <percent>
+                        require-module diff
+                        diff-parse BEGIN %{
+                            \$in_file = " . escape(perlquote($old_filename)) . ";
+                            \$in_file_line = $old_line;
+                        } END $SQ$SQ
+                            print \"execute-keys -client $ENV{client} \${diff_line}g<a-h>$ENV{cursor_column}l;\";
+                            printf \"evaluate-commands -client $ENV{client} $SQ$SQ$SQ$SQ
+                                hook -once window NormalIdle .* $SQ$SQ$SQ$SQ$SQ$SQ$SQ$SQ
+                                    execute-keys vv
+                                    echo -markup -- %s
+                                $SQ$SQ$SQ$SQ$SQ$SQ$SQ$SQ
+                            $SQ$SQ$SQ$SQ ;\"," . escape(escape(perlquote(escape(escape(quote($info)))))) . ";
+                        $SQ$SQ
+                    $SQ
+                ";
+                printf "on_close_fifo=%s show_git_cmd_output %s",
+                    shellquote($on_close_fifo), $show_diff;
+            }
+        ')"
+    }
+
     case "$1" in
         apply)
             shift
@@ -401,7 +572,10 @@ define-command -params 1.. \
             ;;
         blame)
             shift
-            run_git_blame "$@"
+            blame_toggle "$@"
+            ;;
+        blame-jump)
+            blame_jump
             ;;
         hide-blame)
             hide_blame