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thodg/got/tog/tog.c

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  • Author : Stefan Sperling
    Date : 2018-05-20 19:08:05
    Hash : 61e69b96
    Message : better trimming of lines to the right length in tog diff

  • tog/tog.c
  • /*
     * Copyright (c) 2018 Stefan Sperling <stsp@openbsd.org>
     *
     * Permission to use, copy, modify, and distribute this software for any
     * purpose with or without fee is hereby granted, provided that the above
     * copyright notice and this permission notice appear in all copies.
     *
     * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
     * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
     * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
     * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
     * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
     * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
     * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
     */
    
    #include <sys/queue.h>
    
    #include <errno.h>
    #define _XOPEN_SOURCE_EXTENDED
    #include <curses.h>
    #undef _XOPEN_SOURCE_EXTENDED
    #include <panel.h>
    #include <locale.h>
    #include <stdlib.h>
    #include <stdio.h>
    #include <getopt.h>
    #include <string.h>
    #include <err.h>
    #include <unistd.h>
    #include <util.h>
    #include <limits.h>
    #include <wchar.h>
    
    #include "got_error.h"
    #include "got_object.h"
    #include "got_reference.h"
    #include "got_repository.h"
    #include "got_diff.h"
    #include "got_opentemp.h"
    
    #ifndef MIN
    #define	MIN(_a,_b) ((_a) < (_b) ? (_a) : (_b))
    #endif
    
    #ifndef nitems
    #define nitems(_a)	(sizeof((_a)) / sizeof((_a)[0]))
    #endif
    
    struct tog_cmd {
    	const char *name;
    	const struct got_error *(*cmd_main)(int, char *[]);
    	void (*cmd_usage)(void);
    	const char *descr;
    };
    
    __dead static void	usage(void);
    __dead static void	usage_log(void);
    __dead static void	usage_diff(void);
    __dead static void	usage_blame(void);
    
    static const struct got_error*	cmd_log(int, char *[]);
    static const struct got_error*	cmd_diff(int, char *[]);
    static const struct got_error*	cmd_blame(int, char *[]);
    
    static struct tog_cmd tog_commands[] = {
    	{ "log",	cmd_log,	usage_log,
    	    "show repository history" },
    	{ "diff",	cmd_diff,	usage_diff,
    	    "compare files and directories" },
    	{ "blame",	cmd_blame,	usage_blame,
    	    "show line-by-line file history" },
    };
    
    static struct tog_view {
    	WINDOW *window;
    	PANEL *panel;
    } tog_log_view, tog_diff_view;
    
    static const struct got_error *
    show_diff_view(struct got_object *, struct got_object *,
        struct got_repository *);
    static const struct got_error *
    show_log_view(struct got_object_id *, struct got_repository *);
    
    __dead static void
    usage_log(void)
    {
    	endwin();
    	fprintf(stderr, "usage: %s log [-c commit] [repository-path]\n",
    	    getprogname());
    	exit(1);
    }
    
    static const struct got_error *
    draw_commit(struct got_commit_object *commit, struct got_object_id *id)
    {
    	const struct got_error *err = NULL;
    	char *logmsg0 = NULL, *logmsg = NULL;
    	char *author0 = NULL, *author = NULL;
    	char *newline, *smallerthan;
    	char *line = NULL;
    	char *id_str = NULL;
    	const size_t id_display_len = 8;
    	const size_t author_display_len = 16;
    	size_t id_len, author_len, logmsg_len, avail;
    	int i, col;
    
    	err = got_object_id_str(&id_str, id);
    	if (err)
    		return err;
    	id_len = strlen(id_str);
    
    	logmsg0 = strdup(commit->logmsg);
    	if (logmsg0 == NULL) {
    		err = got_error_from_errno();
    		goto done;
    	}
    	logmsg = logmsg0;
    	while (*logmsg == '\n')
    		logmsg++;
    	newline = strchr(logmsg, '\n');
    	if (newline)
    		*newline = '\0';
    	logmsg_len = strlen(logmsg);
    
    	author0 = strdup(commit->author);
    	if (author0 == NULL) {
    		err = got_error_from_errno();
    		goto done;
    	}
    	author = author0;
    	smallerthan = strchr(author, '<');
    	if (smallerthan)
    		*smallerthan = '\0';
    	else {
    		char *at = strchr(author, '@');
    		if (at)
    			*at = '\0';
    	}
    	author_len = strlen(author);
    
    	avail = COLS - 1;
    	line = calloc(avail + 1, sizeof(*line));
    	if (line == NULL) {
    		err = got_error_from_errno();
    		goto done;
    	}
    
    	col = 0;
    	for (i = 0; i < MIN(id_display_len, id_len); i++) {
    		if (col >= avail)
    			goto draw;
    		line[col++] = id_str[i];
    	}
    	while (i < id_display_len) {
    		if (col >= avail)
    			goto draw;
    		line[col++] = ' ';
    		i++;
    	}
    	if (col >= avail)
    		goto draw;
    	line[col++] = ' ';
    	for (i = 0; i < MIN(author_display_len, author_len); i++) {
    		if (col >= avail)
    			goto draw;
    		line[col++] = author[i];
    	}
    	while (i < author_display_len) {
    		if (col >= avail)
    			goto draw;
    		line[col++] = ' ';
    		i++;
    	}
    	if (col >= avail)
    		goto draw;
    	line[col++] = ' ';
    
    	while (col < avail && *logmsg)
    		line[col++] = *logmsg++;
    	while (col < avail)
    		line[col++] = ' ';
    draw:
    	waddstr(tog_log_view.window, line);
    	waddch(tog_log_view.window, '\n');
    done:
    	free(logmsg0);
    	free(author0);
    	free(line);
    	free(id_str);
    	return err;
    }
    
    struct commit_queue_entry {
    	TAILQ_ENTRY(commit_queue_entry) entry;
    	struct got_object_id *id;
    	struct got_commit_object *commit;
    };
    TAILQ_HEAD(commit_queue, commit_queue_entry);
    
    static struct commit_queue_entry *
    alloc_commit_queue_entry(struct got_commit_object *commit,
        struct got_object_id *id)
    {
    	struct commit_queue_entry *entry;
    
    	entry = calloc(1, sizeof(*entry));
    	if (entry == NULL)
    		return NULL;
    
    	entry->id = id;
    	entry->commit = commit;
    	return entry;
    }
    
    static void
    pop_commit(struct commit_queue *commits)
    {
    	struct commit_queue_entry *entry;
    
    	entry = TAILQ_FIRST(commits);
    	TAILQ_REMOVE(commits, entry, entry);
    	got_object_commit_close(entry->commit);
    	free(entry->id);
    	free(entry);
    }
    
    static void
    free_commits(struct commit_queue *commits)
    {
    	while (!TAILQ_EMPTY(commits))
    		pop_commit(commits);
    }
    
    static const struct got_error *
    fetch_parent_commit(struct commit_queue_entry **pentry,
        struct commit_queue_entry *entry, struct got_repository *repo)
    {
    	const struct got_error *err = NULL;
    	struct got_object *obj = NULL;
    	struct got_commit_object *commit;
    	struct got_object_id *id;
    	struct got_parent_id *pid;
    
    	*pentry = NULL;
    
    	/* Follow the first parent (TODO: handle merge commits). */
    	pid = SIMPLEQ_FIRST(&entry->commit->parent_ids);
    	if (pid == NULL)
    		return NULL;
    	err = got_object_open(&obj, repo, pid->id);
    	if (err)
    		return err;
    	if (got_object_get_type(obj) != GOT_OBJ_TYPE_COMMIT) {
    		err = got_error(GOT_ERR_OBJ_TYPE);
    		got_object_close(obj);
    		return err;
    	}
    
    	err = got_object_commit_open(&commit, repo, obj);
    	got_object_close(obj);
    	if (err)
    		return err;
    
    	id = got_object_id_dup(pid->id);
    	if (id == NULL) {
    		err = got_error_from_errno();
    		got_object_commit_close(commit);
    		return err;;
    	}
    
    	*pentry = alloc_commit_queue_entry(commit, id);
    	if (*pentry == NULL) {
    		err = got_error_from_errno();
    		got_object_commit_close(commit);
    	}
    
    	return err;;
    }
    
    static const struct got_error *
    get_head_commit_id(struct got_object_id **head_id, struct got_repository *repo)
    {
    	const struct got_error *err = NULL;
    	struct got_reference *head_ref;
    
    	*head_id = NULL;
    
    	err = got_ref_open(&head_ref, repo, GOT_REF_HEAD);
    	if (err)
    		return err;
    
    	err = got_ref_resolve(head_id, repo, head_ref);
    	got_ref_close(head_ref);
    	if (err) {
    		*head_id = NULL;
    		return err;
    	}
    
    	return NULL;
    }
    
    static const struct got_error *
    prepend_commits(int *ncommits, struct commit_queue *commits,
        struct got_object_id *first_id, struct got_object_id *last_id,
        int limit, struct got_repository *repo)
    {
    	const struct got_error *err = NULL;
    	struct got_object *first_obj = NULL, *last_obj = NULL;
    	struct got_commit_object *commit = NULL;
    	struct got_object_id *id = NULL;
    	struct commit_queue_entry *entry, *old_head_entry;
    
    	*ncommits = 0;
    
    	err = got_object_open(&first_obj, repo, first_id);
    	if (err)
    		goto done;
    	if (got_object_get_type(first_obj) != GOT_OBJ_TYPE_COMMIT) {
    		err = got_error(GOT_ERR_OBJ_TYPE);
    		goto done;
    	}
    	err = got_object_open(&last_obj, repo, last_id);
    	if (err)
    		goto done;
    	if (got_object_get_type(last_obj) != GOT_OBJ_TYPE_COMMIT) {
    		err = got_error(GOT_ERR_OBJ_TYPE);
    		goto done;
    	}
    
    	err = got_object_commit_open(&commit, repo, first_obj);
    	if (err)
    		goto done;
    
    	id = got_object_id_dup(first_id);
    	if (id == NULL) {
    		err = got_error_from_errno();
    		goto done;
    	}
    
    	entry = alloc_commit_queue_entry(commit, id);
    	if (entry == NULL)
    		return got_error_from_errno();
    
    	old_head_entry = TAILQ_FIRST(commits);
    	if (old_head_entry)
    		TAILQ_INSERT_BEFORE(old_head_entry, entry, entry);
    	else
    		TAILQ_INSERT_HEAD(commits, entry, entry);
    
    	*ncommits = 1;
    
    	/*
    	 * Fetch parent commits.
    	 * XXX If first and last commit aren't ancestrally related this loop
    	 * we will keep iterating until a root commit is encountered.
    	 */
    	while (1) {
    		struct commit_queue_entry *pentry;
    
    		err = fetch_parent_commit(&pentry, entry, repo);
    		if (err)
    			goto done;
    		if (pentry == NULL)
    			break;
    
    		/*
    		 * Fill up to old HEAD commit if commit queue was not empty.
    		 * We must not leave a gap in history.
    		 */
    		if (old_head_entry &&
    		    got_object_id_cmp(pentry->id, old_head_entry->id) == 0)
    			break;
    
    		TAILQ_INSERT_AFTER(commits, entry, pentry, entry);
    		(*ncommits)++;
    		if (*ncommits >= limit)
    			break;
    
    		/* Fill up to last requested commit if queue was empty. */
    		if (old_head_entry == NULL &&
    		    got_object_id_cmp(pentry->id, last_id) == 0)
    			break;
    
    		entry = pentry;
    	}
    
    done:
    	if (first_obj)
    		got_object_close(first_obj);
    	if (last_obj)
    		got_object_close(last_obj);
    	return err;
    }
    
    static const struct got_error *
    fetch_commits(struct commit_queue_entry **start_entry,
        struct got_object_id *start_id, struct commit_queue *commits,
        int limit, struct got_repository *repo)
    {
    	const struct got_error *err;
    	struct commit_queue_entry *entry;
    	int ncommits = 0;
    	struct got_object_id *head_id = NULL;
    
    	*start_entry = NULL;
    
    	err = get_head_commit_id(&head_id, repo);
    	if (err)
    		return err;
    
    	/* Prepend HEAD commit and all ancestors up to start commit. */
    	err = prepend_commits(&ncommits, commits, head_id, start_id, limit,
    	    repo);
    	if (err)
    		return err;
    
    	if (got_object_id_cmp(head_id, start_id) == 0)
    		*start_entry = TAILQ_FIRST(commits);
    	else
    		*start_entry = TAILQ_LAST(commits, commit_queue);
    
    	if (ncommits >= limit)
    		return NULL;
    
    	/* Append more commits from start commit up to the requested limit. */
    	entry = TAILQ_LAST(commits, commit_queue);
    	while (entry && ncommits < limit) {
    		struct commit_queue_entry *pentry;
    
    		err = fetch_parent_commit(&pentry, entry, repo);
    		if (err)
    			break;
    		if (pentry)
    			TAILQ_INSERT_TAIL(commits, pentry, entry);
    		entry = pentry;
    		ncommits++;
    	}
    
    	if (err)
    		*start_entry = NULL;
    	return err;
    }
    
    static const struct got_error *
    draw_commits(struct commit_queue_entry **last, struct commit_queue_entry **selected,
        struct commit_queue_entry *first, int selected_idx, int limit)
    {
    	const struct got_error *err = NULL;
    	struct commit_queue_entry *entry;
    	int ncommits = 0;
    
    	werase(tog_log_view.window);
    
    	entry = first;
    	*last = first;
    	while (entry) {
    		if (ncommits == limit)
    			break;
    		if (ncommits == selected_idx) {
    			wstandout(tog_log_view.window);
    			*selected = entry;
    		}
    		err = draw_commit(entry->commit, entry->id);
    		if (ncommits == selected_idx)
    			wstandend(tog_log_view.window);
    		if (err)
    			break;
    		ncommits++;
    		*last = entry;
    		entry = TAILQ_NEXT(entry, entry);
    	}
    
    	update_panels();
    	doupdate();
    
    	return err;
    }
    
    static void
    scroll_up(struct commit_queue_entry **first_displayed_entry, int maxscroll,
        struct commit_queue *commits)
    {
    	struct commit_queue_entry *entry;
    	int nscrolled = 0;
    
    	entry = TAILQ_FIRST(commits);
    	if (*first_displayed_entry == entry)
    		return;
    
    	entry = *first_displayed_entry;
    	while (entry && nscrolled < maxscroll) {
    		entry = TAILQ_PREV(entry, commit_queue, entry);
    		if (entry) {
    			*first_displayed_entry = entry;
    			nscrolled++;
    		}
    	}
    }
    
    static const struct got_error *
    scroll_down(struct commit_queue_entry **first_displayed_entry, int maxscroll,
        struct commit_queue_entry *last_displayed_entry,
        struct commit_queue *commits, struct got_repository *repo)
    {
    	const struct got_error *err = NULL;
    	struct commit_queue_entry *pentry;
    	int nscrolled = 0;
    
    	do {
    		pentry = TAILQ_NEXT(last_displayed_entry, entry);
    		if (pentry == NULL) {
    			err = fetch_parent_commit(&pentry,
    			    last_displayed_entry, repo);
    			if (err || pentry == NULL)
    				break;
    			TAILQ_INSERT_TAIL(commits, pentry, entry);
    		}
    		last_displayed_entry = pentry;
    
    		pentry = TAILQ_NEXT(*first_displayed_entry, entry);
    		if (pentry == NULL)
    			break;
    		*first_displayed_entry = pentry;
    	} while (++nscrolled < maxscroll);
    
    	return err;
    }
    
    static int
    num_parents(struct commit_queue_entry *entry)
    {
    	int nparents = 0;
    
    	while (entry) {
    		entry = TAILQ_NEXT(entry, entry);
    		nparents++;
    	}
    
    	return nparents;
    }
    
    static const struct got_error *
    show_commit(struct commit_queue_entry *entry, struct got_repository *repo)
    {
    	const struct got_error *err;
    	struct commit_queue_entry *pentry;
    	struct got_object *obj1 = NULL, *obj2 = NULL;
    
    	err = got_object_open(&obj2, repo, entry->id);
    	if (err)
    		return err;
    
    	pentry = TAILQ_NEXT(entry, entry);
    	if (pentry == NULL) {
    		err = fetch_parent_commit(&pentry, entry, repo);
    		if (err)
    			return err;
    	}
    	if (pentry) {
    		err = got_object_open(&obj1, repo, pentry->id);
    		if (err)
    			goto done;
    	}
    
    	err = show_diff_view(obj1, obj2, repo);
    done:
    	if (obj1)
    		got_object_close(obj1);
    	if (obj2)
    		got_object_close(obj2);
    	return err;
    }
    
    static const struct got_error *
    show_log_view(struct got_object_id *start_id, struct got_repository *repo)
    {
    	const struct got_error *err = NULL;
    	struct got_object_id *id;
    	int ch, done = 0, selected = 0, nparents;
    	struct commit_queue commits;
    	struct commit_queue_entry *first_displayed_entry = NULL;
    	struct commit_queue_entry *last_displayed_entry = NULL;
    	struct commit_queue_entry *selected_entry = NULL;
    
    	id = got_object_id_dup(start_id);
    	if (id == NULL)
    		return got_error_from_errno();
    
    	if (tog_log_view.window == NULL) {
    		tog_log_view.window = newwin(0, 0, 0, 0);
    		if (tog_log_view.window == NULL)
    			return got_error_from_errno();
    		keypad(tog_log_view.window, TRUE);
    	}
    	if (tog_log_view.panel == NULL) {
    		tog_log_view.panel = new_panel(tog_log_view.window);
    		if (tog_log_view.panel == NULL)
    			return got_error_from_errno();
    	} else
    		show_panel(tog_log_view.panel);
    
    	TAILQ_INIT(&commits);
    	err = fetch_commits(&first_displayed_entry, id, &commits, LINES, repo);
    	if (err)
    		goto done;
    	while (!done) {
    		err = draw_commits(&last_displayed_entry, &selected_entry,
    		    first_displayed_entry, selected, LINES);
    		if (err)
    			goto done;
    
    		nodelay(stdscr, FALSE);
    		ch = wgetch(tog_log_view.window);
    		nodelay(stdscr, TRUE);
    		switch (ch) {
    			case ERR:
    				if (errno) {
    					err = got_error_from_errno();
    					goto done;
    				}
    				break;
    			case 'q':
    				done = 1;
    				break;
    			case 'k':
    			case KEY_UP:
    				if (selected > 0)
    					selected--;
    				if (selected > 0)
    					break;
    				scroll_up(&first_displayed_entry, 1, &commits);
    				break;
    			case KEY_PPAGE:
    				if (TAILQ_FIRST(&commits) ==
    				    first_displayed_entry) {
    					selected = 0;
    					break;
    				}
    				scroll_up(&first_displayed_entry, LINES,
    				    &commits);
    				break;
    			case 'j':
    			case KEY_DOWN:
    				nparents = num_parents(first_displayed_entry);
    				if (selected < LINES - 1 &&
    				    selected < nparents - 1) {
    					selected++;
    					break;
    				}
    				err = scroll_down(&first_displayed_entry, 1,
    				    last_displayed_entry, &commits, repo);
    				if (err)
    					goto done;
    				break;
    			case KEY_NPAGE:
    				err = scroll_down(&first_displayed_entry, LINES,
    				    last_displayed_entry, &commits, repo);
    				if (err)
    					goto done;
    				if (last_displayed_entry->commit->nparents > 0)
    					break;
    				/* can't scroll any further; move cursor down */
    				nparents = num_parents(first_displayed_entry);
    				if (selected < LINES - 1 ||
    				    selected < nparents - 1)
    					selected = MIN(LINES - 1, nparents - 1);
    				break;
    			case KEY_RESIZE:
    				if (selected > LINES)
    					selected = LINES - 1;
    				break;
    			case KEY_ENTER:
    			case '\r':
    				err = show_commit(selected_entry, repo);
    				if (err)
    					break;
    				show_panel(tog_log_view.panel);
    				break;
    			default:
    				break;
    		}
    	}
    done:
    	free_commits(&commits);
    	return err;
    }
    
    static const struct got_error *
    cmd_log(int argc, char *argv[])
    {
    	const struct got_error *error;
    	struct got_repository *repo;
    	struct got_object_id *start_id = NULL;
    	char *repo_path = NULL;
    	char *start_commit = NULL;
    	int ch;
    
    #ifndef PROFILE
    	if (pledge("stdio rpath wpath cpath flock proc tty", NULL) == -1)
    		err(1, "pledge");
    #endif
    
    	while ((ch = getopt(argc, argv, "c:")) != -1) {
    		switch (ch) {
    		case 'c':
    			start_commit = optarg;
    			break;
    		default:
    			usage();
    			/* NOTREACHED */
    		}
    	}
    
    	argc -= optind;
    	argv += optind;
    
    	if (argc == 0) {
    		repo_path = getcwd(NULL, 0);
    		if (repo_path == NULL)
    			return got_error_from_errno();
    	} else if (argc == 1) {
    		repo_path = realpath(argv[0], NULL);
    		if (repo_path == NULL)
    			return got_error_from_errno();
    	} else
    		usage_log();
    
    	error = got_repo_open(&repo, repo_path);
    	free(repo_path);
    	if (error != NULL)
    		return error;
    
    	if (start_commit == NULL) {
    		error = get_head_commit_id(&start_id, repo);
    		if (error != NULL)
    			return error;
    	} else {
    		struct got_object *obj;
    		error = got_object_open_by_id_str(&obj, repo, start_commit);
    		if (error == NULL) {
    			start_id = got_object_get_id(obj);
    			if (start_id == NULL)
    				error = got_error_from_errno();
    		}
    	}
    	if (error != NULL)
    		return error;
    	error = show_log_view(start_id, repo);
    	free(start_id);
    	got_repo_close(repo);
    	return error;
    }
    
    __dead static void
    usage_diff(void)
    {
    	endwin();
    	fprintf(stderr, "usage: %s diff [repository-path] object1 object2\n",
    	    getprogname());
    	exit(1);
    }
    
    static char *
    parse_next_line(FILE *f, size_t *len)
    {
    	char *line;
    	size_t linelen;
    	size_t lineno;
    	const char delim[3] = { '\0', '\0', '\0'};
    
    	line = fparseln(f, &linelen, &lineno, delim, 0);
    	if (len)
    		*len = linelen;
    	return line;
    }
    
    /* Format a line for display, ensuring that it won't overflow COLS columns. */
    static const struct got_error *
    format_line(wchar_t **wlinep, char *line)
    {
    	const struct got_error *err = NULL;
    	int cols = 0;
    	wchar_t *wline = NULL;
    	size_t wlen;
    	int i;
    
    	*wlinep = NULL;
    
    	wlen = mbstowcs(NULL, line, 0);
    	if (wlen == (size_t)-1)
    		return got_error_from_errno();
    
    	wline = calloc(wlen + 1, sizeof(wchar_t));
    	if (wline == NULL)
    		return got_error_from_errno();
    
    	if (mbstowcs(wline, line, wlen) != wlen) {
    		err = got_error_from_errno();
    		goto done;
    	}
    
    	i = 0;
    	while (i < wlen && cols <= COLS) {
    		int width = wcwidth(wline[i]);
    		switch (width) {
    		case 0:
    			break;
    		case 1:
    		case 2:
    			cols += width;
    			break;
    		case -1:
    			if (wline[i] == L'\t')
    				cols += TABSIZE;
    			break;
    		default:
    			err = got_error_from_errno();
    			goto done;
    		}
    		if (cols <= COLS)
    			i++;
    	}
    	wline[i] = L'\0';
    done:
    	if (err)
    		free(wline);
    	else
    		*wlinep = wline;
    	return err;
    }
    
    static const struct got_error *
    draw_diff(FILE *f, int *first_displayed_line, int *last_displayed_line,
        int *eof, int max_lines)
    {
    	const struct got_error *err;
    	int nlines = 0, nprinted = 0;
    	char *line;
    	size_t len;
    	wchar_t *wline;
    
    	rewind(f);
    	werase(tog_diff_view.window);
    
    	*eof = 0;
    	while (nprinted < max_lines) {
    		line = parse_next_line(f, &len);
    		if (line == NULL) {
    			*eof = 1;
    			break;
    		}
    		if (++nlines < *first_displayed_line) {
    			free(line);
    			continue;
    		}
    
    		err = format_line(&wline, line);
    		if (err) {
    			free(line);
    			return err;
    		}
    		waddwstr(tog_diff_view.window, wline);
    		waddch(tog_diff_view.window, '\n');
    		if (++nprinted == 1)
    			*first_displayed_line = nlines;
    		free(line);
    	}
    	*last_displayed_line = nlines;
    
    	update_panels();
    	doupdate();
    
    	return NULL;
    }
    
    static const struct got_error *
    show_diff_view(struct got_object *obj1, struct got_object *obj2,
        struct got_repository *repo)
    {
    	const struct got_error *err;
    	FILE *f;
    	int ch, done = 0, first_displayed_line = 1, last_displayed_line = LINES;
    	int eof, i;
    
    	if (obj1 != NULL && obj2 != NULL &&
    	    got_object_get_type(obj1) != got_object_get_type(obj2))
    		return got_error(GOT_ERR_OBJ_TYPE);
    
    	f = got_opentemp();
    	if (f == NULL)
    		return got_error_from_errno();
    
    	switch (got_object_get_type(obj1 ? obj1 : obj2)) {
    	case GOT_OBJ_TYPE_BLOB:
    		err = got_diff_objects_as_blobs(obj1, obj2, repo, f);
    		break;
    	case GOT_OBJ_TYPE_TREE:
    		err = got_diff_objects_as_trees(obj1, obj2, repo, f);
    		break;
    	case GOT_OBJ_TYPE_COMMIT:
    		err = got_diff_objects_as_commits(obj1, obj2, repo, f);
    		break;
    	default:
    		return got_error(GOT_ERR_OBJ_TYPE);
    	}
    
    	fflush(f);
    
    	if (tog_diff_view.window == NULL) {
    		tog_diff_view.window = newwin(0, 0, 0, 0);
    		if (tog_diff_view.window == NULL)
    			return got_error_from_errno();
    		keypad(tog_diff_view.window, TRUE);
    	}
    	if (tog_diff_view.panel == NULL) {
    		tog_diff_view.panel = new_panel(tog_diff_view.window);
    		if (tog_diff_view.panel == NULL)
    			return got_error_from_errno();
    	} else
    		show_panel(tog_diff_view.panel);
    
    	while (!done) {
    		err = draw_diff(f, &first_displayed_line, &last_displayed_line,
    		    &eof, LINES);
    		if (err)
    			break;
    		nodelay(stdscr, FALSE);
    		ch = wgetch(tog_diff_view.window);
    		nodelay(stdscr, TRUE);
    		switch (ch) {
    			case 'q':
    				done = 1;
    				break;
    			case 'k':
    			case KEY_UP:
    			case KEY_BACKSPACE:
    				if (first_displayed_line > 1)
    					first_displayed_line--;
    				break;
    			case KEY_PPAGE:
    				i = 0;
    				while (i++ < LINES - 1 &&
    				    first_displayed_line > 1)
    					first_displayed_line--;
    				break;
    			case 'j':
    			case KEY_DOWN:
    			case KEY_ENTER:
    			case '\r':
    				if (!eof)
    					first_displayed_line++;
    				break;
    			case KEY_NPAGE:
    			case ' ':
    				i = 0;
    				while (!eof && i++ < LINES - 1) {
    					char *line = parse_next_line(f, NULL);
    					first_displayed_line++;
    					if (line == NULL)
    						break;
    				}
    				break;
    			default:
    				break;
    		}
    	}
    	fclose(f);
    	return err;
    }
    
    static const struct got_error *
    cmd_diff(int argc, char *argv[])
    {
    	const struct got_error *error = NULL;
    	struct got_repository *repo = NULL;
    	struct got_object *obj1 = NULL, *obj2 = NULL;
    	char *repo_path = NULL;
    	char *obj_id_str1 = NULL, *obj_id_str2 = NULL;
    	int ch;
    
    #ifndef PROFILE
    	if (pledge("stdio rpath wpath cpath flock proc tty", NULL) == -1)
    		err(1, "pledge");
    #endif
    
    	while ((ch = getopt(argc, argv, "")) != -1) {
    		switch (ch) {
    		default:
    			usage();
    			/* NOTREACHED */
    		}
    	}
    
    	argc -= optind;
    	argv += optind;
    
    	if (argc == 0) {
    		usage_diff(); /* TODO show local worktree changes */
    	} else if (argc == 2) {
    		repo_path = getcwd(NULL, 0);
    		if (repo_path == NULL)
    			return got_error_from_errno();
    		obj_id_str1 = argv[0];
    		obj_id_str2 = argv[1];
    	} else if (argc == 3) {
    		repo_path = realpath(argv[0], NULL);
    		if (repo_path == NULL)
    			return got_error_from_errno();
    		obj_id_str1 = argv[1];
    		obj_id_str2 = argv[2];
    	} else
    		usage_diff();
    
    	error = got_repo_open(&repo, repo_path);
    	free(repo_path);
    	if (error)
    		goto done;
    
    	error = got_object_open_by_id_str(&obj1, repo, obj_id_str1);
    	if (error)
    		goto done;
    
    	error = got_object_open_by_id_str(&obj2, repo, obj_id_str2);
    	if (error)
    		goto done;
    
    	error = show_diff_view(obj1, obj2, repo);
    done:
    	got_repo_close(repo);
    	if (obj1)
    		got_object_close(obj1);
    	if (obj2)
    		got_object_close(obj2);
    	return error;
    }
    
    __dead static void
    usage_blame(void)
    {
    	endwin();
    	fprintf(stderr, "usage: %s blame [repository-path] blob-object\n",
    	    getprogname());
    	exit(1);
    }
    
    static const struct got_error *
    cmd_blame(int argc, char *argv[])
    {
    	return got_error(GOT_ERR_NOT_IMPL);
    }
    
    static void
    init_curses(void)
    {
    	initscr();
    	cbreak();
    	noecho();
    	nonl();
    	intrflush(stdscr, FALSE);
    	keypad(stdscr, TRUE);
    	curs_set(0);
    }
    
    __dead static void
    usage(void)
    {
    	int i;
    
    	fprintf(stderr, "usage: %s [-h] [command] [arg ...]\n\n"
    	    "Available commands:\n", getprogname());
    	for (i = 0; i < nitems(tog_commands); i++) {
    		struct tog_cmd *cmd = &tog_commands[i];
    		fprintf(stderr, "    %s: %s\n", cmd->name, cmd->descr);
    	}
    	exit(1);
    }
    
    static char **
    make_argv(const char *arg0, const char *arg1)
    {
    	char **argv;
    	int argc = (arg1 == NULL ? 1 : 2);
    
    	argv = calloc(argc, sizeof(char *));
    	if (argv == NULL)
    		err(1, "calloc");
    	argv[0] = strdup(arg0);
    	if (argv[0] == NULL)
    		err(1, "calloc");
    	if (arg1) {
    		argv[1] = strdup(arg1);
    		if (argv[1] == NULL)
    			err(1, "calloc");
    	}
    
    	return argv;
    }
    
    int
    main(int argc, char *argv[])
    {
    	const struct got_error *error = NULL;
    	struct tog_cmd *cmd = NULL;
    	int ch, hflag = 0;
    	char **cmd_argv = NULL;
    
    	setlocale(LC_ALL, "");
    
    	while ((ch = getopt(argc, argv, "h")) != -1) {
    		switch (ch) {
    		case 'h':
    			hflag = 1;
    			break;
    		default:
    			usage();
    			/* NOTREACHED */
    		}
    	}
    
    	argc -= optind;
    	argv += optind;
    	optind = 0;
    	optreset = 1;
    
    	if (argc == 0) {
    		/* Build an argument vector which runs a default command. */
    		cmd = &tog_commands[0];
    		cmd_argv = make_argv(cmd->name, NULL);
    		argc = 1;
    	} else {
    		int i;
    
    		/* Did the user specific a command? */
    		for (i = 0; i < nitems(tog_commands); i++) {
    			if (strncmp(tog_commands[i].name, argv[0],
    			    strlen(argv[0])) == 0) {
    				cmd = &tog_commands[i];
    				if (hflag)
    					tog_commands[i].cmd_usage();
    				break;
    			}
    		}
    		if (cmd == NULL) {
    			/* Did the user specify a repository? */
    			char *repo_path = realpath(argv[0], NULL);
    			if (repo_path) {
    				struct got_repository *repo;
    				error = got_repo_open(&repo, repo_path);
    				if (error == NULL)
    					got_repo_close(repo);
    			} else
    				error = got_error_from_errno();
    			if (error) {
    				fprintf(stderr, "%s: '%s' is neither a known "
    				    "command nor a path to a repository\n",
    				    getprogname(), argv[0]);
    				free(repo_path);
    				return 1;
    			}
    			cmd = &tog_commands[0];
    			cmd_argv = make_argv(cmd->name, repo_path);
    			argc = 2;
    			free(repo_path);
    		}
    	}
    
    	init_curses();
    
    	error = cmd->cmd_main(argc, cmd_argv ? cmd_argv : argv);
    	if (error)
    		goto done;
    done:
    	endwin();
    	free(cmd_argv);
    	if (error)
    		fprintf(stderr, "%s: %s\n", getprogname(), error->msg);
    	return 0;
    }