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, 26 insertions, 28 deletions

diff --git a/save-xml.c b/save-xml.c
index 56de154fe..7801080e9 100644
--- a/save-xml.c
+++ b/save-xml.c
@@ -5,6 +5,7 @@
 #include <errno.h>
 #include <time.h>
 #include <unistd.h>
+#include <fcntl.h>
 
 #include "dive.h"
 #include "device.h"
@@ -210,18 +211,6 @@ static void save_overview(struct membuffer *b, struct dive *dive)
 	show_utf8(b, dive->suit, "  <suit>", "</suit>\n", 0);
 }
 
-static int nr_cylinders(struct dive *dive)
-{
-	int nr;
-
-	for (nr = MAX_CYLINDERS; nr; --nr) {
-		cylinder_t *cylinder = dive->cylinder + nr - 1;
-		if (!cylinder_nodata(cylinder))
-			break;
-	}
-	return nr;
-}
-
 static void save_cylinder_info(struct membuffer *b, struct dive *dive)
 {
 	int i, nr;
@@ -251,18 +240,6 @@ static void save_cylinder_info(struct membuffer *b, struct dive *dive)
 	}
 }
 
-static int nr_weightsystems(struct dive *dive)
-{
-	int nr;
-
-	for (nr = MAX_WEIGHTSYSTEMS; nr; --nr) {
-		weightsystem_t *ws = dive->weightsystem + nr - 1;
-		if (!weightsystem_none(ws))
-			break;
-	}
-	return nr;
-}
-
 static void save_weightsystem_info(struct membuffer *b, struct dive *dive)
 {
 	int i, nr;
@@ -609,15 +586,12 @@ static void save_backup(const char *name, const char *ext, const char *new_ext)
 	free(newname);
 }
 
-void save_dives_logic(const char *filename, const bool select_only)
+static void try_to_backup(const char *filename)
 {
-	struct membuffer buf = { 0 };
-	FILE *f;
 	char extension[][5] = { "xml", "ssrf", "" };
 	int i = 0;
 	int flen = strlen(filename);
 
-	save_dives_buffer(&buf, select_only);
 	/* Maybe we might want to make this configurable? */
 	while (extension[i][0] != '\0') {
 		int elen = strlen(extension[i]);
@@ -627,6 +601,30 @@ void save_dives_logic(const char *filename, const bool select_only)
 		}
 		i++;
 	}
+}
+
+void save_dives_logic(const char *filename, const bool select_only)
+{
+	struct membuffer buf = { 0 };
+	FILE *f;
+	int fd;
+
+	/*
+	 * See if the file already exists, and if so,
+	 * perhaps it's a git save-file pointer?
+	 *
+	 * Otherwise, try to back it up.
+	 */
+	fd = subsurface_open(filename, O_RDONLY, 0);
+	if (fd >= 0) {
+		if (git_save_dives(fd, select_only))
+			return;
+		close(fd);
+		try_to_backup(filename);
+	}
+
+	save_dives_buffer(&buf, select_only);
+
 	f = subsurface_fopen(filename, "w");
 	if (f) {
 		flush_buffer(&buf, f);