Initial implementation of git save format

This saves the dive data into a git object repository instead of a
single XML file.

We create a git object tree with each dive as a separate file,
hierarchically by trip and date.

NOTE 1: This largely duplicates the XML saving code, because trying to
share it seemed just too painful: the logic is very similar, but the
details of the actual strings end up differing sufficiently that there
are tons of trivial differences.

The git save format is line-based with minimal quoting, while XML quotes
everything with either "<..\>" or using single quotes around attributes.

NOTE 2: You currently need a dummy "file" to save to, which points to
the real save location: the git repository and branch to be used.  We
should make this a config thing, but for testing, do something like
this:

	echo git /home/torvalds/scuba:linus > git-test

to create that git information file, and when you use "Save To" and
specify "git-test" as the file to save to, subsurface will use the new
git save logic to save to the branch "linus" in the repository found at
"/home/torvalds/scuba".

NOTE 3: The git save format uses just the git object directory, it does
*not* check out the result in any git working tree or index.  So after
you do a save, you can do

     git log -p linus

to see what actually happened in that branch, but it will not affect any
actual checked-out state in the repository.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>

1 files changed, 689 insertions, 0 deletions

diff --git a/save-git.c b/save-git.c
new file mode 100644
index 000000000..6e0d989c0
--- /dev/null
+++ b/save-git.c
@@ -0,0 +1,689 @@
+#include <stdio.h>
+#include <ctype.h>
+#include <string.h>
+#include <stdlib.h>
+#include <errno.h>
+#include <time.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <git2.h>
+
+#include "dive.h"
+#include "device.h"
+#include "membuffer.h"
+
+#define VA_BUF(b, fmt) do { va_list args; va_start(args, fmt); put_vformat(b, fmt, args); va_end(args); } while (0)
+
+static void cond_put_format(int cond, struct membuffer *b, const char *fmt, ...)
+{
+	if (cond) {
+		VA_BUF(b, fmt);
+	}
+}
+
+#define SAVE(str, x) cond_put_format(dive->x, b, str " %d\n", dive->x)
+
+static void put_degrees(struct membuffer *b, degrees_t value, const char sep)
+{
+	int udeg = value.udeg;
+	const char *sign = "";
+
+	if (udeg < 0) {
+		udeg = -udeg;
+		sign = "-";
+	}
+	put_format(b,"%s%u.%06u%c", sign, FRACTION(udeg, 1000000), sep);
+}
+
+static void show_gps(struct membuffer *b, degrees_t latitude, degrees_t longitude)
+{
+	if (latitude.udeg || longitude.udeg) {
+		put_string(b, "gps ");
+		put_degrees(b, latitude, ' ');
+		put_degrees(b, longitude, '\n');
+	}
+}
+
+static void quote(struct membuffer *b, const char *text)
+{
+	const char *p = text;
+
+	for (;;) {
+		const char *escape;
+
+		switch (*p++) {
+		default:
+			continue;
+		case 0:
+			escape = NULL;
+			break;
+		case 1 ... 8:
+		case 11:
+		case 12:
+		case 14 ... 31:
+			escape = "?";
+			break;
+		case '"':
+			escape = "\\\"";
+			break;
+		case '\n':
+			escape = "\n\t";
+			if (*p == '\n')
+				escape = "\n";
+			break;
+		}
+		put_bytes(b, text, (p - text - 1));
+		if (!escape)
+			break;
+		put_string(b, escape);
+		text = p;
+	}
+}
+
+static void show_utf8(struct membuffer *b, const char *prefix, const char *value, const char *postfix)
+{
+	if (value) {
+		put_format(b, "%s\"", prefix);
+		quote(b, value);
+		put_format(b, "\"%s", postfix);
+	}
+}
+
+static void save_overview(struct membuffer *b, struct dive *dive)
+{
+	show_gps(b, dive->latitude, dive->longitude);
+	show_utf8(b, "location ", dive->location, "\n");
+	show_utf8(b, "divemaster ", dive->divemaster, "\n");
+	show_utf8(b, "buddy ", dive->buddy, "\n");
+	show_utf8(b, "suit ", dive->suit, "\n");
+	show_utf8(b, "notes ", dive->notes, "\n");
+}
+
+static void save_tags(struct membuffer *b, struct tag_entry *tags)
+{
+	const char *sep = " ";
+
+	if (!tags)
+		return;
+	/* The first entry is a dummy, because people don't understand pointers to pointers */
+	tags = tags->next;
+	if (!tags)
+		return;
+	put_string(b, "tags");
+	while (tags) {
+		show_utf8(b, sep, tags->tag->source ? : tags->tag->name, "");
+		sep = ", ";
+		tags = tags->next;
+	}
+	put_string(b, "\n");
+}
+
+static void save_cylinder_info(struct membuffer *b, struct dive *dive)
+{
+	int i, nr;
+
+	nr = nr_cylinders(dive);
+	for (i = 0; i < nr; i++) {
+		cylinder_t *cylinder = dive->cylinder + i;
+		int volume = cylinder->type.size.mliter;
+		const char *description = cylinder->type.description;
+		int o2 = cylinder->gasmix.o2.permille;
+		int he = cylinder->gasmix.he.permille;
+
+		put_string(b, "cylinder");
+		if (volume)
+			put_milli(b, " vol=", volume, "l");
+		put_pressure(b, cylinder->type.workingpressure, " workpressure=", "bar");
+		show_utf8(b, " description=", description, "");
+		strip_mb(b);
+		if (o2) {
+			put_format(b, " o2=%u.%u%%", FRACTION(o2, 10));
+			if (he)
+				put_format(b, " he=%u.%u%%", FRACTION(he, 10));
+		}
+		put_pressure(b, cylinder->start, " start=", "bar");
+		put_pressure(b, cylinder->end, " end=", "bar");
+		put_string(b, "\n");
+	}
+}
+
+static void save_weightsystem_info(struct membuffer *b, struct dive *dive)
+{
+	int i, nr;
+
+	nr = nr_weightsystems(dive);
+	for (i = 0; i < nr; i++) {
+		weightsystem_t *ws = dive->weightsystem + i;
+		int grams = ws->weight.grams;
+		const char *description = ws->description;
+
+		put_string(b, "weightsystem");
+		put_milli(b, " weight=", grams, "kg");
+		show_utf8(b, " description=", description, "");
+		put_string(b, "\n");
+	}
+}
+
+static void save_dive_temperature(struct membuffer *b, struct dive *dive)
+{
+	if (!dive->airtemp.mkelvin && !dive->watertemp.mkelvin)
+		return;
+	if (dive->airtemp.mkelvin == dc_airtemp(&dive->dc) && dive->watertemp.mkelvin == dc_watertemp(&dive->dc))
+		return;
+
+	put_string(b, "divetemperature");
+	if (dive->airtemp.mkelvin != dc_airtemp(&dive->dc))
+		put_temperature(b, dive->airtemp, " air=", "°C");
+	if (dive->watertemp.mkelvin != dc_watertemp(&dive->dc))
+		put_temperature(b, dive->watertemp, " water=", "°C'");
+	put_string(b, "\n");
+}
+
+static void save_depths(struct membuffer *b, struct divecomputer *dc)
+{
+	/* What's the point of this dive entry again? */
+	if (!dc->maxdepth.mm && !dc->meandepth.mm)
+		return;
+
+	put_string(b, "  depth");
+	put_depth(b, dc->maxdepth, " max=", "m");
+	put_depth(b, dc->meandepth, " mean=", "m");
+	put_string(b, "\n");
+}
+
+static void save_temperatures(struct membuffer *b, struct divecomputer *dc)
+{
+	if (!dc->airtemp.mkelvin && !dc->watertemp.mkelvin)
+		return;
+	put_string(b, "  temperature");
+	put_temperature(b, dc->airtemp, " air=", "°C");
+	put_temperature(b, dc->watertemp, " water=", "°C");
+	put_string(b, "\n");
+}
+
+static void save_airpressure(struct membuffer *b, struct divecomputer *dc)
+{
+	if (!dc->surface_pressure.mbar)
+		return;
+	put_string(b, "  surface");
+	put_pressure(b, dc->surface_pressure, " pressure=", "bar");
+	put_string(b, "\n");
+}
+
+static void save_salinity(struct membuffer *b, struct divecomputer *dc)
+{
+	/* only save if we have a value that isn't the default of sea water */
+	if (!dc->salinity || dc->salinity == SEAWATER_SALINITY)
+		return;
+	put_string(b, "  water");
+	put_salinity(b, dc->salinity, " salinity=", "g/l");
+	put_string(b, "\n");
+}
+
+static void show_date(struct membuffer *b, timestamp_t when)
+{
+	struct tm tm;
+
+	utc_mkdate(when, &tm);
+
+	put_format(b, " date=%04u-%02u-%02u",
+		   tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday);
+	put_format(b, " time=%02u:%02u:%02u",
+		   tm.tm_hour, tm.tm_min, tm.tm_sec);
+}
+
+static void show_index(struct membuffer *b, int value, const char *pre, const char *post)
+{
+	if (value)
+		put_format(b, " %s%d%s", pre, value, post);
+}
+
+/*
+ * Samples are saved as densely as possible while still being readable,
+ * since they are the bulk of the data.
+ *
+ * For parsing, look at the units to figure out what the numbers are.
+ */
+static void save_sample(struct membuffer *b, struct sample *sample, struct sample *old)
+{
+	put_format(b, "  %3u:%02umin", FRACTION(sample->time.seconds, 60));
+	put_milli(b, " ", sample->depth.mm, "m");
+	put_temperature(b, sample->temperature, " ", "°C");
+	put_pressure(b, sample->cylinderpressure, " ", "bar");
+
+	/*
+	 * We only show sensor information for samples with pressure, and only if it
+	 * changed from the previous sensor we showed.
+	 */
+	if (sample->cylinderpressure.mbar && sample->sensor != old->sensor) {
+		put_format(b, " sensor=%d", sample->sensor);
+		old->sensor = sample->sensor;
+	}
+
+	/* the deco/ndl values are stored whenever they change */
+	if (sample->ndl.seconds != old->ndl.seconds) {
+		put_format(b, " ndl=%u:%02umin", FRACTION(sample->ndl.seconds, 60));
+		old->ndl = sample->ndl;
+	}
+	if (sample->in_deco != old->in_deco) {
+		put_format(b, " in_deco=%d", sample->in_deco ? 1 : 0);
+		old->in_deco = sample->in_deco;
+	}
+	if (sample->stoptime.seconds != old->stoptime.seconds) {
+		put_format(b, " stoptime=%u:%02umin", FRACTION(sample->stoptime.seconds, 60));
+		old->stoptime = sample->stoptime;
+	}
+
+	if (sample->stopdepth.mm != old->stopdepth.mm) {
+		put_milli(b, " stopdepth=", sample->stopdepth.mm, "m");
+		old->stopdepth = sample->stopdepth;
+	}
+
+	if (sample->cns != old->cns) {
+		put_format(b, " cns=%u%%", sample->cns);
+		old->cns = sample->cns;
+	}
+
+	if (sample->po2 != old->po2) {
+		put_milli(b, " po2=", sample->po2, "bar");
+		old->po2 = sample->po2;
+	}
+	show_index(b, sample->heartbeat, "heartbeat=", "");
+	show_index(b, sample->bearing, "bearing=", "°");
+	put_format(b, "\n");
+}
+
+static void save_samples(struct membuffer *b, int nr, struct sample *s)
+{
+	struct sample dummy = {};
+
+	while (--nr >= 0) {
+		save_sample(b, s, &dummy);
+		s++;
+	}
+}
+
+static void save_one_event(struct membuffer *b, struct event *ev)
+{
+	put_format(b, "  event %d:%02dmin", FRACTION(ev->time.seconds, 60));
+	show_index(b, ev->type, "type=", "");
+	show_index(b, ev->flags, "flags=", "");
+	show_index(b, ev->value, "value=", "");
+	show_utf8(b, ev->name, " name=", "");
+	put_string(b, "\n");
+}
+
+static void save_events(struct membuffer *b, struct event *ev)
+{
+	while (ev) {
+		save_one_event(b, ev);
+		ev = ev->next;
+	}
+}
+
+static void save_dc(struct membuffer *b, struct dive *dive, struct divecomputer *dc)
+{
+	put_format(b, "divecomputer");
+	show_utf8(b, " model=", dc->model, "");
+	if (dc->deviceid)
+		put_format(b, " deviceid=%08x", dc->deviceid);
+	if (dc->diveid)
+		put_format(b, " diveid=%08x", dc->diveid);
+	if (dc->when && dc->when != dive->when)
+		show_date(b, dc->when);
+	if (dc->duration.seconds && dc->duration.seconds != dive->dc.duration.seconds)
+		put_duration(b, dc->duration, " duration=", "min");
+	put_string(b, "\n");
+
+	save_depths(b, dc);
+	save_temperatures(b, dc);
+	save_airpressure(b, dc);
+	save_salinity(b, dc);
+	put_duration(b, dc->surfacetime, "  surfacetime", "min\n");
+
+	save_events(b, dc->events);
+	save_samples(b, dc->samples, dc->sample);
+}
+
+/*
+ * Note that we don't save the date and time or dive
+ * number: they are encoded in the filename.
+ */
+static void create_dive_buffer(struct dive *dive, struct membuffer *b)
+{
+	struct divecomputer *dc;
+
+	put_format(b, "duration %u:%02u min\n", FRACTION(dive->dc.duration.seconds, 60));
+	SAVE("rating", rating);
+	SAVE("visibility", visibility);
+	cond_put_format(dive->tripflag == NO_TRIP, b, "notrip\n");
+	save_tags(b, dive->tag_list);
+
+	save_overview(b, dive);
+	save_cylinder_info(b, dive);
+	save_weightsystem_info(b, dive);
+	save_dive_temperature(b, dive);
+
+	/* Save the dive computer data */
+	dc = &dive->dc;
+	do {
+		save_dc(b, dive, dc);
+		dc = dc->next;
+	} while (dc);
+}
+
+static int git_save_error(const char *fmt, ...)
+{
+	struct membuffer b = { 0 };
+	VA_BUF(&b, fmt);
+
+	/* We should do some UI element thing describing the failure */
+	put_bytes(&b, "\n", 1);
+	flush_buffer(&b, stderr);
+	free_buffer(&b);
+
+	return -1;
+}
+
+/*
+ * libgit2 has a "git_treebuilder" concept, but it's broken, and can not
+ * be used to do a flat tree (like the git "index") nor a recursive tree.
+ * Stupid.
+ *
+ * So we have to do that "keep track of recursive treebuilder entries"
+ * ourselves. We use 'git_treebuilder' for any regular files, and our own
+ * data structures for recursive trees.
+ *
+ * When finally writing it out, we traverse the subdirectories depth-
+ * first, writing them out, and then adding the written-out trees to
+ * the git_treebuilder they existed in.
+ */
+struct dir {
+	git_treebuilder *files;
+	struct dir *subdirs, *sibling;
+	char name[1];
+};
+
+/*
+ * The name of a dive is the date plus a hash of the contents.
+ */
+static void generate_name(struct dive *dive, git_oid *id, struct membuffer *name)
+{
+	struct tm tm;
+
+	utc_mkdate(dive->when, &tm);
+	put_format(name, "%04u-%02u-%02u-%02u:%02u:%02u",
+		tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday,
+		tm.tm_hour, tm.tm_min, tm.tm_sec);
+	cond_put_format(dive->number, name, "-%d", dive->number);
+	put_format(name, "-%02x%02x%02x%02x%c",
+		id->id[0], id->id[1], id->id[2], id->id[3], 0);
+}
+
+static int save_one_dive(git_repository *repo, struct dir *tree, struct dive *dive)
+{
+	struct membuffer buf = { 0 }, name = { 0 };
+	git_oid blob_id;
+	int ret;
+
+	create_dive_buffer(dive, &buf);
+	ret = git_blob_create_frombuffer(&blob_id, repo, buf.buffer, buf.len);
+	free_buffer(&buf);
+	if (ret)
+		return git_save_error("git blob creation failed");
+
+	generate_name(dive, &blob_id, &name);
+	ret = git_treebuilder_insert(NULL, tree->files, name.buffer, &blob_id, 0100644);
+	free_buffer(&name);
+	if (ret)
+		return git_save_error("git tree insert failed");
+
+	return 0;
+}
+
+/*
+ * This does *not* make sure the new subdirectory doesn't
+ * alias some existing name. Currently we always create
+ * unique subdirectory names ("tripXYZ"), but ..
+ */
+static struct dir *new_directory(struct dir *parent, const char *fmt, ...)
+{
+	struct membuffer name = { 0 };
+	struct dir *subdir;
+
+	VA_BUF(&name, fmt);
+	subdir = malloc(sizeof(*subdir)+name.len);
+
+	/*
+	 * It starts out empty: no subdirectories of its own,
+	 * and an empty treebuilder list of files.
+	 */
+	subdir->subdirs = NULL;
+	git_treebuilder_create(&subdir->files, NULL);
+	memcpy(subdir->name, name.buffer, name.len);
+	subdir->name[name.len] = 0;
+
+	/* Add it to the list of subdirs of the parent */
+	subdir->sibling = parent->subdirs;
+	parent->subdirs = subdir;
+
+	return subdir;
+}
+
+static int save_one_trip(git_repository *repo, struct dir *tree, dive_trip_t *trip, int idx)
+{
+	int i;
+	struct dive *dive;
+	struct dir *subdir;
+
+	subdir = new_directory(tree, "trip%03d", idx);
+	for_each_dive(i, dive) {
+		if (dive->divetrip == trip)
+			save_one_dive(repo, subdir, dive);
+	}
+
+	return 0;
+}
+
+#define TRIPNAME_SIZE (10)
+
+static int create_git_tree(git_repository *repo, struct dir *tree, bool select_only)
+{
+	int i, tripidx;
+	struct dive *dive;
+	dive_trip_t *trip;
+
+	tripidx = 0;
+	for (trip = dive_trip_list; trip != NULL; trip = trip->next)
+		trip->index = 0;
+
+	/* save the dives */
+	for_each_dive(i, dive) {
+		trip = dive->divetrip;
+
+		if (select_only) {
+			if (!dive->selected)
+				continue;
+			/* We don't save trips when doing selected dive saves */
+			trip = NULL;
+		}
+
+		if (trip) {
+			/* Did we already save this trip? */
+			if (trip->index)
+				continue;
+			trip->index = ++tripidx;
+
+			/* Pass that new subdirectory in for save-trip */
+			save_one_trip(repo, tree, trip, tripidx);
+			continue;
+		}
+
+		save_one_dive(repo, tree, dive);
+	}
+	return 0;
+}
+
+/*
+ * libgit2 revision 0.19 and earlier do not have the signature and
+ * message log arguments.
+ */
+#if !LIBGIT2_VER_MAJOR && LIBGIT2_VER_MINOR <= 19
+  #define git_branch_create(out,repo,branch_name,target,force,sig,msg) \
+	git_branch_create(out,repo,branch_name,target,force)
+  #define git_reference_set_target(out,ref,target,signature,log_message) \
+	git_reference_set_target(out,ref,target)
+#endif
+
+static int create_new_commit(git_repository *repo, const char *branch, git_oid *tree_id)
+{
+	int ret;
+	git_reference *ref;
+	git_object *parent;
+	git_oid commit_id;
+	git_signature *author;
+	git_commit *commit;
+	git_tree *tree;
+
+	ret = git_branch_lookup(&ref, repo, branch, GIT_BRANCH_LOCAL);
+	switch (ret) {
+	default:
+		return git_save_error("Bad branch '%s' (%s)", branch, strerror(errno));
+	case GIT_EINVALIDSPEC:
+		return git_save_error("Invalid branch name '%s'", branch);
+	case GIT_ENOTFOUND: /* We'll happily create it */
+		ref = NULL; parent = NULL;
+		break;
+	case 0:
+		if (git_reference_peel(&parent, ref, GIT_OBJ_COMMIT))
+			return git_save_error("Unable to look up parent in branch '%s'", branch);
+		/* all good */
+		break;
+	}
+
+	if (git_tree_lookup(&tree, repo, tree_id))
+		return git_save_error("Could not look up newly created tree");
+
+	/* git_signature_default() is too recent */
+	if (git_signature_now(&author, "Subsurface", "subsurface@hohndel.org"))
+		return git_save_error("No user name configuration in git repo");
+
+	if (git_commit_create_v(&commit_id, repo, NULL, author, author, NULL, "subsurface commit", tree, parent != NULL, parent))
+		return git_save_error("Git commit create failed (%s)", strerror(errno));
+
+	if (git_commit_lookup(&commit, repo, &commit_id))
+		return git_save_error("Could not look up newly created commit");
+
+	if (!ref) {
+		if (git_branch_create(&ref, repo, branch, commit, 0, author, "Create branch"))
+			return git_save_error("Failed to create branch '%s'", branch);
+	}
+	if (git_reference_set_target(&ref, ref, &commit_id, author, "Subsurface save event"))
+		return git_save_error("Failed to update branch '%s'", branch);
+
+	return 0;
+}
+
+static int write_git_tree(git_repository *repo, struct dir *tree, git_oid *result)
+{
+	int ret;
+	struct dir *subdir;
+
+	/* Write out our subdirectories, add them to the treebuilder, and free them */
+	while ((subdir = tree->subdirs) != NULL) {
+		git_oid id;
+
+		if (!write_git_tree(repo, subdir, &id))
+			git_treebuilder_insert(NULL, tree->files, subdir->name, &id, 0040000);
+		tree->subdirs = subdir->sibling;
+		free(subdir);
+	};
+
+	/* .. write out the resulting treebuilder */
+	ret = git_treebuilder_write(result, repo, tree->files);
+
+	/* .. and free the now useless treebuilder */
+	git_treebuilder_free(tree->files);
+
+	return ret;
+}
+
+static int do_git_save(git_repository *repo, const char *branch, bool select_only)
+{
+	struct dir tree;
+	git_oid id;
+
+	/* Start with an empty tree: no subdirectories, no files */
+	tree.name[0] = 0;
+	tree.subdirs = NULL;
+	if (git_treebuilder_create(&tree.files, NULL))
+		return git_save_error("git treebuilder failed");
+
+	/* Populate our tree data structure */
+	if (create_git_tree(repo, &tree, select_only))
+		return -1;
+
+	if (write_git_tree(repo, &tree, &id))
+		return git_save_error("git tree write failed");
+
+	/* And save the tree! */
+	create_new_commit(repo, branch, &id);
+	return 0;
+}
+
+int git_save_dives(int fd, bool select_only)
+{
+	int len, ret;
+	struct stat st;
+	static char buffer[2048];
+	git_repository *repo;
+	char *loc, *branch;
+
+	if (fstat(fd, &st) < 0)
+		return 0;
+	if (st.st_size >= sizeof(buffer))
+		return 0;
+	len = st.st_size;
+	if (read(fd, buffer, len) != len)
+		return 0;
+	buffer[len] = 0;
+	if (len < 4)
+		return 0;
+	if (memcmp(buffer, "git ", 4))
+		return 0;
+
+	/* Ok, it's a git pointer, we're going to follow it */
+	close(fd);
+
+	/* Trim any whitespace at the end */
+	while (isspace(buffer[len-1]))
+		buffer[--len] = 0;
+
+	/* skip the "git" part and any whitespace from the beginning */
+	loc = buffer+3;
+	len -= 3;
+	while (isspace(*loc)) {
+		loc++;
+		len--;
+	}
+
+	if (!len)
+		return git_save_error("Invalid git pointer");
+
+	/*
+	 * The result should be a git directory and branch name, like
+	 *  "/home/torvalds/scuba:linus"
+	 */
+	branch = strrchr(loc, ':');
+	if (branch)
+		*branch++ = 0;
+
+	if (git_repository_open(&repo, loc))
+		return git_save_error("Unable to open git repository at '%s' (branch '%s')", loc, branch);
+
+	ret = do_git_save(repo, branch, select_only);
+	git_repository_free(repo);
+	return ret < 0 ? ret : 1;
+}