eeshow/: move file and history access to file/

eeshow/file/file.c

@@ -0,0 +1,248 @@
+/*
+ * file/file.c - Open and read a file
+ *
+ * Written 2016 by Werner Almesberger
+ * Copyright 2016 by Werner Almesberger
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ */
+
+#include <stddef.h>
+#include <stdbool.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+
+#include "util.h"
+#include "diag.h"
+#include "file/git-file.h"
+#include "file/file.h"
+
+
+void *file_oid(const struct file *file)
+{
+	if (!file->vcs)
+		return NULL;
+	return vcs_git_get_oid(file->vcs);
+}
+
+
+bool file_oid_eq(const void *a, const void *b)
+{
+	/*
+	 * If both a and b are NULL, we don't have revision data and thus
+	 * can't tell if they're identical.
+	 */
+	return a && b && vcs_git_oid_eq(a, b);
+}
+
+
+bool file_cat(const struct file *file, void *user, const char *line)
+{
+	printf("%s\n", line);
+	return 1;
+}
+
+
+char *file_graft_relative(const char *base, const char *name)
+{
+	const char *slash;
+	char *res;
+	unsigned len;
+
+	if (*name == '/')
+		return NULL;
+
+	slash = strrchr(base, '/');
+	if (!slash)
+		return NULL;
+
+	len = slash + 1 - base;
+	res = alloc_size(len + strlen(name) + 1);
+	memcpy(res, base, len);
+	strcpy(res + len, name);
+
+	return res;
+}
+
+
+static bool try_related(struct file *file)
+{
+	char *tmp;
+
+	if (!file->related)
+		return 0;
+
+	tmp = file_graft_relative(file->related->name, file->name);
+	if (!tmp)
+		return NULL;
+
+	if (*file->name == '/')
+		return 0;
+
+	file->file = fopen(tmp, "r");
+	if (!file->file) {
+		free(tmp);
+		return 0;
+	}
+
+	progress(1, "reading %s\n", tmp);
+
+	free((char *) file->name);
+	file->name = tmp;
+	return 1;
+}
+
+
+/*
+ * @@@ logic isn't quite complete yet. It should go something like this:
+ *
+ * - if there is no related item,
+ *   - try file,
+ *   - if there is a colon, try VCS,
+ *   - give up
+ * - if there is a related item,
+ *   - if it is a VCS,
+ *     - try the revision matching or predating (if different repo) that of the
+ *       related repo,
+ (     - fall through and try as if it was a file
+ *   - try opening as file. If this fails,
+ *     - if the name of the file to open is absolute, give up
+ *     - try `dirname related`/file_ope_open
+ *     - give up
+ *
+ * @@@ should we see if non-VCS file is in a VCS ? E.g.,
+ * /home/my-libs/foo.lib 1234:/home/my-project/foo.sch
+ * or maybe use : as indictor for VCS, i.e.,
+ * :/home/my-libs/foo.lib ...
+ *
+ * @@@ explicit revision should always win over related.
+ */
+
+static void *open_vcs(struct file *file)
+{
+	char *colon;
+
+	colon = strchr(file->name, ':');
+	if (colon) {
+		char *tmp;
+
+		tmp = stralloc(file->name);
+		tmp[colon - file->name] = 0;
+		file->vcs = vcs_git_open(tmp, colon + 1,
+		    file->related ? file->related->vcs : NULL);
+		if (file->vcs) {
+			free(tmp);
+			return file->vcs;
+		}
+		progress(2, "could not open %s:%s\n", tmp, colon + 1);
+		return NULL;
+	} else {
+		file->vcs = vcs_git_open(NULL, file->name,
+		    file->related ? file->related->vcs : NULL);
+		if (file->vcs)
+			return file->vcs;
+		progress(2, "could not open %s\n", file->name);
+		return NULL;
+	}
+}
+
+
+static void file_init(struct file *file, const char *name,
+    const struct file *related)
+{
+	file->name = stralloc(name);
+	file->lineno = 0;
+	file->related = related;
+	file->file = NULL;
+	file->vcs = NULL;
+}
+
+
+bool file_open(struct file *file, const char *name, const struct file *related)
+{
+	file_init(file, name, related);
+
+	if (related && related->vcs) {
+		file->vcs = open_vcs(file);
+		if (file->vcs)
+			return 1;
+	}
+
+	file->file = fopen(name, "r");
+	if (file->file) {
+		progress(1, "reading %s\n", name);
+		return 1;
+	}
+
+	if (try_related(file))
+		return 1;
+
+	if (verbose)
+		diag_perror(name);
+
+	if (!strchr(name, ':')) {
+		if (!verbose)
+			diag_perror(name);
+		goto fail;
+	}
+
+	file->vcs = open_vcs(file);
+	if (file->vcs)
+		return 1;
+
+	error("could not open %s\n", name);
+fail:
+	free((char *) file->name);
+	return 0;
+}
+
+
+bool file_open_revision(struct file *file, const char *rev, const char *name,
+    const struct file *related)
+{
+	if (!rev)
+		return file_open(file, name, related);
+
+	file_init(file, name, related);
+	file->vcs = vcs_git_open(rev, name, related ? related->vcs : NULL);
+	if (file->vcs)
+		return 1;
+	progress(2, "could not open %s at %s\n", name, rev);
+	return 0;
+}
+
+
+bool file_read(struct file *file,
+    bool (*parse)(const struct file *file, void *user, const char *line),
+    void *user)
+{
+	static char *buf = NULL;
+	static size_t n = 0;
+	char *nl;
+
+	if (file->vcs)
+		return vcs_read(file->vcs, file, parse, user);
+	while (getline(&buf, &n, file->file) > 0) {
+		nl = strchr(buf, '\n');
+		if (nl)
+			*nl = 0;
+		file->lineno++;
+		if (!parse(file, user, buf))
+			return 0;
+	}
+	return 1;
+}
+
+
+void file_close(struct file *file)
+{
+	if (file->file)
+		fclose(file->file);
+	if (file->vcs)
+		vcs_close(file->vcs);
+	free((char *) file->name);
+}

eeshow/file/file.h

@@ -0,0 +1,45 @@
+/*
+ * file/file.h - Open and read a file
+ *
+ * Written 2016 by Werner Almesberger
+ * Copyright 2016 by Werner Almesberger
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ */
+
+#ifndef FILE_FILE_H
+#define	FILE_FILE_H
+
+#include <stdbool.h>
+#include <stdio.h>
+
+
+struct file {
+	FILE *file;		/* NULL if using a version control system */
+	void *vcs;		/* VCS descriptor or NULL */
+	const char *name;	/* name/designator given to file_open */
+	unsigned lineno;
+	const struct file *related; /* NULL if not related to anything */
+};
+
+
+void *file_oid(const struct file *file);
+bool file_oid_eq(const void *a, const void *b);
+
+bool file_cat(const struct file *file, void *user, const char *line);
+
+char *file_graft_relative(const char *base, const char *name);
+
+bool file_open(struct file *file, const char *name,
+    const struct file *related);
+bool file_open_revision(struct file *file, const char *rev, const char *name,
+    const struct file *related);
+bool file_read(struct file *file,
+    bool (*parse)(const struct file *file, void *user, const char *line),
+    void *user);
+void file_close(struct file *file);
+
+#endif /* !FILE_FILE_H */

eeshow/file/git-file.c

@@ -0,0 +1,502 @@
+/*
+ * file/git-file.c - Open and read a file from git version control system
+ *
+ * Written 2016 by Werner Almesberger
+ * Copyright 2016 by Werner Almesberger
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ */
+
+#define	_GNU_SOURCE	/* for get_current_dir_name */
+#include <stdlib.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <string.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+
+#include <git2.h>
+
+#include "util.h"
+#include "diag.h"
+#include "file/file.h"
+#include "file/git-util.h"
+#include "file/git-file.h"
+
+
+struct vcs_git {
+	const char *name;
+	const char *revision;
+	const struct vcs_git *related;
+
+	git_repository *repo;
+	git_tree *tree;
+	git_object *obj;
+
+	const void *data;
+	unsigned size;
+};
+
+
+/* ----- OID matching ------------------------------------------------------ */
+
+
+void *vcs_git_get_oid(const void *ctx)
+{
+	const struct vcs_git *vcs_git = ctx;
+	struct git_oid *new;
+
+	new = alloc_type(git_oid);
+	git_oid_cpy(new, git_object_id(vcs_git->obj));
+	return new;
+}
+
+
+bool vcs_git_oid_eq(const void *a, const void *b)
+{
+	return !git_oid_cmp(a, b);
+}
+
+
+/* ----- Open -------------------------------------------------------------- */
+
+
+static git_repository *select_repo(const char *path)
+{
+	git_repository *repo = NULL;
+	char *tmp = stralloc(path);
+	char *slash;
+
+	/*
+	 * If we can't find a repo, this may be due to the file or directory
+	 * the path points to not existing in the currently checked-out tree.
+	 * So we trim off elements until we find a repository.
+	 */
+	while (1) {
+		progress(3, "trying \"%s\"\n", tmp);
+		if (!git_repository_open_ext(&repo, *tmp ? tmp : "/",
+		    GIT_REPOSITORY_OPEN_CROSS_FS, NULL))
+			break;
+		slash = strrchr(tmp, '/');
+		if (!slash)
+			break;
+		*slash = 0;
+	}
+	free(tmp);
+	return repo;
+}
+
+
+static git_tree *pick_revision(git_repository *repo, const char *revision)
+{
+	git_commit *commit;
+	git_object *obj;
+	git_tree *tree;
+
+	if (git_revparse_single(&obj, repo, revision)) {
+		const git_error *e = giterr_last();
+
+		fatal("%s: %s\n", git_repository_path(repo), e->message);
+	}
+
+	if (git_object_type(obj) != GIT_OBJ_COMMIT)
+		fatal("%s: not a commit\n", revision);
+	commit = (git_commit *) obj;
+
+	if (git_commit_tree(&tree, commit)) {
+		const git_error *e = giterr_last();
+
+		fatal("%s: %s\n", revision, e->message);
+	}
+
+	return tree;
+}
+
+
+static char *canonical_path_into_repo(const char *repo_dir, const char *path)
+{
+	struct stat repo_st, path_st;
+	char *tmp, *tmp2, *slash, *tail, *real;
+	char *to;
+	const char *end, *from;
+
+	/* identify inode of repo root */
+
+	if (stat(repo_dir, &repo_st) < 0)
+		diag_pfatal(repo_dir);
+	if (!S_ISDIR(repo_st.st_mode))
+		fatal("%s: not a directory\n", repo_dir);
+
+	/* convert relative paths to absolute */
+
+	if (*path == '/') {
+		tmp = stralloc(path);
+	} else {
+		char *cwd = get_current_dir_name();
+
+		tmp = alloc_size(strlen(cwd) + 1 + strlen(path) + 1);
+		sprintf(tmp, "%s/%s", cwd, path);
+		free(cwd);
+	}
+
+	/* remove trailing / */
+
+	slash = strrchr(tmp, '/');
+	if (slash && slash != tmp && !slash[1])
+		*slash = 0;
+
+	/*
+	 * If path does point to inexistent object, separate into the part that
+	 * is valid on the current system and the tail containing dead things.
+	 */
+	end = tail = strchr(tmp, 0);
+
+	while (1) {
+		progress(3, "probing \"%s\" tail \"%s\"\n", tmp, tail);
+		if (stat(tmp, &path_st) == 0)
+			break;
+		if (!tmp[1])
+			fatal("%s: cannot resolve\n", path);
+		slash = strrchr(tmp, '/');
+		if (tail != end)
+			tail[-1] = '/';
+		tail = slash + 1;
+		*slash = 0;
+	}
+
+	/* remove . and .. from tail */
+
+	progress(3, "input tail \"%s\"\n", tail);
+	from = to = tail;
+	while (1) {
+		if (!strncmp(from, "./", 2)) {
+			from += 2;
+			continue;
+		}
+		if (!strcmp(from, "."))
+			break;
+		if (strncmp(from, "../", 3) && strcmp(from, "..")) {
+			while (*from) {
+				*to++ = *from++;
+				if (from[-1] == '/')
+					break;
+			}
+			if (!*from)
+				break;
+		}
+
+		/*
+		 * We have something like this:
+		 * /home/repo/dead/../../foo
+		 */
+		if (to == tail)
+			fatal("%s: can't climb out of dead path\n", path);
+
+		/*
+		 * We have something like
+		 * "foo/" -> ""
+		 * or
+		 * "foo/bar/" -> "foo/"
+		 * where "to" points to the end.
+		 */
+		to--;
+		while (to != tail && to[-1] != '/')
+			to--;
+	}
+	*to = 0;
+	progress(3, "output tail \"%s\"\n", tail);
+
+	/* resolve all symlinks */
+
+	real = realpath(tmp, NULL);
+	progress(3, "realpath(\"%s\") = \"%s\"\n", tmp, real);
+
+	/* append tail */
+
+	if (*tail) {
+		tmp2 = alloc_size(strlen(real) + 1 + strlen(tail) + 1);
+		sprintf(tmp2, "%s/%s", real, tail);
+		free(real);
+	} else {
+		tmp2 = real;
+	}
+	free(tmp);
+	tmp = tmp2;
+
+	progress(2, "full object path \"%s\"\n", tmp);
+
+	/* find which part of our path is inside the repo */
+
+	end = tail = strchr(tmp, 0);
+	while (1) {
+		progress(3, "trying \"%s\" tail \"%s\"\n", tmp, tail);
+
+		if (stat(tmp, &path_st) == 0 &&
+		    path_st.st_dev == repo_st.st_dev &&
+		    path_st.st_ino == repo_st.st_ino)
+			break;
+
+		slash = strrchr(tmp, '/');
+
+		/* "this cannot happen" */
+		if (tail == tmp || !slash)
+			fatal("divergent paths:\nrepo \"%s\"\nobject \"%s\"\n",
+			    repo_dir, tail);
+
+		if (tail != end)
+			tail[-1] = '/';
+		tail = slash + 1;
+		*slash = 0;
+	}
+
+	progress(2, "path in repo \"%s\"\n", tail);
+
+	tmp2 = stralloc(tail);
+	free(tmp);
+	return tmp2;
+}
+
+
+static git_tree_entry *find_file(git_repository *repo, git_tree *tree,
+    const char *path)
+{
+	git_tree_entry *entry;
+	char *repo_path = stralloc(git_repository_workdir(repo));
+		/* use workdir, not path, for submodules */
+	char *slash, *canon_path;
+	int len;
+
+	/* remove trailing / from repo_path */
+	slash = strrchr(repo_path, '/');
+	if (slash && slash != repo_path && !slash[1])
+		*slash = 0;
+
+	len = strlen(repo_path);
+	if (len >= 5 && !strcmp(repo_path + len - 5, "/.git"))
+		repo_path[len == 5 ? 1 : len - 5] = 0;
+
+	progress(2, "repo dir \"%s\"\n", repo_path);
+
+	canon_path = canonical_path_into_repo(repo_path, path);
+	free(repo_path);
+
+	if (git_tree_entry_bypath(&entry, tree, canon_path)) {
+		const git_error *e = giterr_last();
+
+		error("%s: %s\n", path, e->message);
+		free(canon_path);
+		return NULL;
+	}
+	free(canon_path);
+
+	return entry;
+}
+
+
+static const void *get_data(struct vcs_git *vcs_git, git_tree_entry *entry,
+    unsigned *size)
+{
+	git_repository *repo =vcs_git->repo;
+	git_object *obj;
+	git_blob *blob;
+
+	if (git_tree_entry_type(entry) != GIT_OBJ_BLOB)
+		fatal("entry is not a blob\n");
+	if (git_tree_entry_to_object(&obj, repo, entry)) {
+		const git_error *e = giterr_last();
+
+		fatal("%s\n", e->message);
+	}
+	vcs_git->obj = obj;
+
+	if (verbose > 2) {
+		git_buf buf = { 0 };
+
+		if (git_object_short_id(&buf, obj))  {
+			const git_error *e = giterr_last();
+
+			fatal("%s\n", e->message);
+		}
+		progress(3, "object %s\n", buf.ptr);
+		git_buf_free(&buf);
+	}
+	blob = (git_blob *) obj;
+	*size = git_blob_rawsize(blob);
+	return git_blob_rawcontent(blob);
+}
+
+
+static bool send_line(const char *s, unsigned len,
+    bool (*parse)(const struct file *file, void *user, const char *line),
+    void *user, const struct file *file)
+{
+	char *tmp = alloc_size(len + 1);
+	bool res;
+
+	memcpy(tmp, s, len);
+	tmp[len] = 0;
+	res = parse(file, user, tmp);
+	free(tmp);
+	return res;
+}
+
+
+static bool access_file_data(struct vcs_git *vcs_git, const char *name)
+{
+	git_tree_entry *entry;
+
+	entry = find_file(vcs_git->repo, vcs_git->tree, name);
+	if (!entry)
+		return 0;
+	progress(1, "reading %s\n", name);
+
+	vcs_git->data = get_data(vcs_git, entry, &vcs_git->size);
+	return 1;
+}
+
+
+static bool related_same_repo(struct vcs_git *vcs_git)
+{
+	const struct vcs_git *related = vcs_git->related;
+
+	vcs_git->repo = related->repo;
+	vcs_git->tree = related->tree;
+
+	return access_file_data(vcs_git, vcs_git->name);
+}
+
+
+static bool related_other_repo(struct vcs_git *vcs_git)
+{
+	static bool shown = 0;
+
+	/* @@@ find revision <= date of revision in related */
+	if (!shown)
+		warning("related_other_repo is not yet implemented\n");
+	shown = 1;
+	return 0;
+}
+
+
+static bool related_only_repo(struct vcs_git *vcs_git)
+{
+	const struct vcs_git *related = vcs_git->related;
+	char *tmp;
+
+	progress(2, "trying graft \"%s\" \"%s\"\n",
+	    related->name, vcs_git->name);
+	tmp = file_graft_relative(related->name, vcs_git->name);
+	if (!tmp)
+		return 0;
+
+	vcs_git->repo = related->repo;
+	vcs_git->tree = related->tree;
+
+	if (!access_file_data(vcs_git, tmp)) {
+		free(tmp);
+		return 0;
+	}
+
+	free((char *) vcs_git->name);
+	vcs_git->name = tmp;
+
+	return 1;
+}
+
+
+static bool try_related(struct vcs_git *vcs_git)
+{
+	if (!vcs_git->related)
+		return 0;
+	if (vcs_git->revision)
+		return 0;
+
+	vcs_git->repo = select_repo(vcs_git->name);
+	if (vcs_git->repo) {
+		if (!strcmp(git_repository_path(vcs_git->related->repo),
+		    git_repository_path(vcs_git->repo)))
+			return related_same_repo(vcs_git);
+		else
+			return related_other_repo(vcs_git);
+	}
+
+	return related_only_repo(vcs_git);
+}
+
+
+struct vcs_git *vcs_git_open(const char *revision, const char *name,
+    const struct vcs_git *related)
+{
+	struct vcs_git *vcs_git = alloc_type(struct vcs_git);
+
+	git_init_once();
+
+	vcs_git->name = stralloc(name);
+	vcs_git->revision = revision ? stralloc(revision) : NULL;
+	vcs_git->related = related;
+
+	if (try_related(vcs_git))
+		return vcs_git;
+
+	vcs_git->repo = select_repo(name);
+	if (!vcs_git->repo) {
+		error("%s: not found\n", name);
+		goto fail;
+	}
+	progress(2, "using repository %s\n",
+	    git_repository_path(vcs_git->repo));
+
+	if (!revision)
+		revision = "HEAD";
+	vcs_git->tree = pick_revision(vcs_git->repo, revision);
+
+	if (!access_file_data(vcs_git, name))
+		goto fail;
+
+	return vcs_git;
+
+fail:
+	vcs_git_close(vcs_git);
+	return 0;
+}
+
+
+/* ----- Read -------------------------------------------------------------- */
+
+
+bool vcs_git_read(void *ctx, struct file *file,
+    bool (*parse)(const struct file *file, void *user, const char *line),
+    void *user)
+{
+	const struct vcs_git *vcs_git = ctx;
+	const char *end = vcs_git->data + vcs_git->size;
+	const char *p = vcs_git->data;
+	const char *nl;
+
+	while (p != end) {
+		nl = memchr(p, '\n', end - p);
+		file->lineno++;
+		if (!nl)
+			return send_line(p, end - p, parse, user, file);
+		if (!send_line(p, nl - p, parse, user, file))
+			return 0;
+		p = nl + 1;
+	}
+	return 1;
+}
+
+
+/* ----- Close ------------------------------------------------------------- */
+
+
+void vcs_git_close(void *ctx)
+{
+	struct vcs_git *vcs_git = ctx;
+
+	free((char *) vcs_git->name);
+	free((char *) vcs_git->revision);
+	free(vcs_git);
+}

eeshow/file/git-file.h

@@ -0,0 +1,45 @@
+/*
+ * file/git-file.h - Open and read a file from git version control system
+ *
+ * Written 2016 by Werner Almesberger
+ * Copyright 2016 by Werner Almesberger
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ */
+
+#ifndef FILE_GIT_FILE_H
+#define	FILE_GIT_FILE_H
+
+#include <stdbool.h>
+
+
+/*
+ * future-proofing: if someone wants to add back-ends for other version control
+ * systems, the identifiers will already be there.
+ */
+
+#define	vcs_open	vcs_git_open
+#define	vcs_read	vcs_git_read
+#define	vcs_close	vcs_git_close
+
+
+struct vcs_git;
+struct file;
+
+
+void vcs_git_init(void);
+
+void *vcs_git_get_oid(const void *ctx);	/* mallocs */
+bool vcs_git_oid_eq(const void *a, const void *b);
+
+struct vcs_git *vcs_git_open(const char *revision, const char *name,
+    const struct vcs_git *related);
+bool vcs_git_read(void *ctx, struct file *file,
+    bool (*parse)(const struct file *file, void *user, const char *line),
+    void *user);
+void vcs_git_close(void *ctx);
+
+#endif /* !FILE_GIT_FILE_H */

eeshow/file/git-hist.c

@@ -0,0 +1,273 @@
+/*
+ * file/git-hist.c - Retrieve revision history from GIT repo
+ *
+ * Written 2016 by Werner Almesberger
+ * Copyright 2016 by Werner Almesberger
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ */
+
+#include <stddef.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <time.h>	/* for vcs_long_for_pango */
+#include <alloca.h>
+
+#include "util.h"
+#include "diag.h"
+#include "file/git-util.h"
+#include "file/git-file.h"
+#include "file/git-hist.h"
+
+
+/*
+ * @@@ we assume to have a single head. That isn't necessarily true, since
+ * each open branch has its own head. Getting this right is for further study.
+ */
+
+
+static struct hist *new_commit(unsigned branch)
+{
+	struct hist *h;
+
+	h = alloc_type(struct hist);
+	h->commit = NULL;
+	h->branch = branch;
+	h->newer = NULL;
+	h->n_newer = 0;
+	h->older = NULL;
+	h->n_older = 0;
+	return h;
+}
+
+
+static void uplink(struct hist *down, struct hist *up)
+{
+	down->newer = realloc(down->newer,
+	    sizeof(struct hist *) * (down->n_newer + 1));
+	if (!down->newer)
+		diag_pfatal("realloc");
+	down->newer[down->n_newer++] = up;
+}
+
+
+static struct hist *find_commit(struct hist *h, const git_commit *commit)
+{
+	unsigned i;
+	struct hist *found;
+
+	/*
+	 * @@@ should probably use
+	 * git_oid_equal(git_object_id(a), git_object_id(b))
+	 */
+	if (h->commit == commit)
+		return h;
+	for (i = 0; i != h->n_older; i++) {
+		if (h->older[i]->newer[0] != h)
+			continue;
+		found = find_commit(h->older[i], commit);
+		if (found)
+			return found;
+	}
+	return NULL;
+}
+
+
+static void recurse(struct hist *h,
+    unsigned n_branches, struct hist **branches)
+{
+	unsigned n, i, j;
+	struct hist **b;
+	const git_error *e;
+
+	n = git_commit_parentcount(h->commit);
+	if (verbose > 2)
+		progress(3, "commit %p: %u + %u\n", h->commit, n_branches, n);
+
+	b = alloca(sizeof(struct hist) * (n_branches - 1 + n));
+	n_branches--;
+	memcpy(b, branches, sizeof(struct hist *) * n_branches);
+
+	h->older = alloc_type_n(struct hist *, n);
+	h->n_older = n;
+
+	for (i = 0; i != n; i++) {
+		git_commit *commit;
+		struct hist *found = NULL;
+
+		if (git_commit_parent(&commit, h->commit, i)) {
+			e = giterr_last();
+			fatal("git_commit_parent: %s\n", e->message);
+		}
+		for (j = 0; j != n_branches; j++) {
+			found = find_commit(b[j], commit);
+			if (found)
+				break;
+		}
+		if (found) {
+			uplink(found, h);
+			h->older[i] = found;
+		} else {
+			struct hist *new;
+
+			new = new_commit(n_branches);
+			new->commit = commit;
+			h->older[i] = new;
+			b[n_branches++] = new;
+			uplink(new, h);
+			recurse(new, n_branches, b);
+		}
+	}
+}
+
+
+bool vcs_git_try(const char *path)
+{
+	git_repository *repo;
+
+	git_init_once();
+
+	if (git_repository_open_ext(&repo, path,
+	    GIT_REPOSITORY_OPEN_CROSS_FS, NULL))
+		return 0;
+	return !git_repository_is_empty(repo);
+}
+
+
+struct hist *vcs_git_hist(const char *path)
+{
+	struct hist *head, *dirty;
+	git_repository *repo;
+	git_oid oid;
+	const git_error *e;
+
+	head = new_commit(0);
+
+	git_init_once();
+
+	if (git_repository_open_ext(&repo, path,
+	    GIT_REPOSITORY_OPEN_CROSS_FS, NULL)) {
+		e = giterr_last();
+		fatal("%s: %s\n", path, e->message);
+	}
+
+	if (git_reference_name_to_id(&oid, repo, "HEAD")) {
+		e = giterr_last();
+		fatal("%s: %s\n", git_repository_path(repo), e->message);
+	}
+
+	if (git_commit_lookup(&head->commit, repo, &oid)) {
+		e = giterr_last();
+		fatal("%s: %s\n", git_repository_path(repo), e->message);
+	}
+
+	recurse(head, 1, &head);
+
+	if (!git_repo_is_dirty(repo))
+		return head;
+
+	dirty = new_commit(0);
+	dirty->older = alloc_type(struct hist *);
+	dirty->older[0] = head;
+	dirty->n_older = 1;
+	uplink(head, dirty);
+
+	return dirty;
+}
+
+
+char *vcs_git_get_rev(struct hist *h)
+{
+	const git_oid *oid = git_commit_id(h->commit);
+	char *s = alloc_size(GIT_OID_HEXSZ + 1);
+
+	return git_oid_tostr(s, GIT_OID_HEXSZ + 1, oid);
+}
+
+
+const char *vcs_git_summary(struct hist *h)
+{
+	const char *summary;
+	const git_error *e;
+
+	if (!h->commit)
+		return "Uncommitted changes";
+	summary = git_commit_summary(h->commit);
+	if (summary)
+		return summary;
+
+	e = giterr_last();
+	fatal("git_commit_summary: %s\n", e->message);
+}
+
+
+/*
+ * @@@ This one is a bit inconvenient. It depends both on the information the
+ * VCS provides, some of which is fairly generic, but some may not be, and
+ * the very specific constraints imposed by the markup format of Pango. 
+ */
+
+char *vcs_git_long_for_pango(struct hist *h,
+    char *(*formatter)(const char *fmt, ...))
+{
+	const git_error *e;
+	git_buf buf = { 0 };
+	time_t commit_time;
+	const git_signature *sig;
+	char *s;
+
+	if (!h->commit)
+		return stralloc("Uncommitted changes");
+	if (git_object_short_id(&buf, (git_object *) h->commit))
+		goto fail;
+	commit_time = git_commit_time(h->commit);
+	sig = git_commit_committer(h->commit);
+	s = formatter("<b>%s</b> %s%s &lt;%s&gt;<small>\n%s</small>",
+	    buf.ptr, ctime(&commit_time), sig->name, sig->email,
+	    git_commit_summary(h->commit));
+	git_buf_free(&buf);
+	return s;
+
+fail:
+	e = giterr_last();
+	fatal("vcs_git_long_for_pango: %s\n", e->message);
+}
+
+
+void hist_iterate(struct hist *h,
+    void (*fn)(void *user, struct hist *h), void *user)
+{
+	unsigned i;
+
+	fn(user, h);
+	for (i = 0; i != h->n_older; i++)
+		if (h->older[i]->newer[h->older[i]->n_newer - 1] == h)
+			hist_iterate(h->older[i], fn, user);
+}
+
+
+void dump_hist(struct hist *h)
+{
+	git_buf buf = { 0 };
+	const git_error *e;
+	unsigned i;
+
+	if (h->commit) {
+		if (git_object_short_id(&buf, (git_object *) h->commit)) {
+			e = giterr_last();
+			fatal("git_object_short_id: %s\n", e->message);
+		}
+		printf("%*s%s  %s\n",
+		    2 * h->branch, "", buf.ptr, vcs_git_summary(h));
+		git_buf_free(&buf);
+	} else {
+		printf("dirty\n");
+	}
+
+	for (i = 0; i != h->n_older; i++)
+		if (h->older[i]->newer[h->older[i]->n_newer - 1] == h)
+			dump_hist(h->older[i]);
+}

eeshow/file/git-hist.h

@@ -0,0 +1,44 @@
+/*
+ * file/git-hist.h - Retrieve revision history from GIT repo
+ *
+ * Written 2016 by Werner Almesberger
+ * Copyright 2016 by Werner Almesberger
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ */
+
+#ifndef FILE_GIT_HIST_H
+#define	FILE_GIT_HIST_H
+
+#include <stdbool.h>
+
+#include <git2.h>
+
+
+struct hist {
+	struct git_commit *commit; /* NULL if uncommitted changes */
+
+	unsigned branch;	/* branch index */
+
+	struct hist **newer;
+	unsigned n_newer;
+
+	struct hist **older;
+	unsigned n_older;
+};
+
+
+bool vcs_git_try(const char *path);
+struct hist *vcs_git_hist(const char *path);
+char *vcs_git_get_rev(struct hist *h);
+const char *vcs_git_summary(struct hist *hist);
+char *vcs_git_long_for_pango(struct hist *hist,
+    char *(*formatter)(const char *fmt, ...));
+void hist_iterate(struct hist *h, 
+    void (*fn)(void *user, struct hist *h), void *user);
+void dump_hist(struct hist *h);
+
+#endif /* !FILE_GIT_HIST_H */

eeshow/file/git-util.c

@@ -0,0 +1,83 @@
+/*
+ * file/git-util.c - Git utility functions
+ *
+ * Written 2016 by Werner Almesberger
+ * Copyright 2016 by Werner Almesberger
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ */
+
+#include <stdbool.h>
+#include <assert.h>
+
+#include <git2.h>
+
+#include "file/git-util.h"
+
+
+/*
+ * This seems to be an efficient way for finding out if a repo is dirty.
+ *
+ * http://ben.straub.cc/2013/04/02/libgit2-checkout/
+ *
+ * References:
+ * https://libgit2.github.com/libgit2/#HEAD/group/checkout/git_checkout_index
+ * https://libgit2.github.com/libgit2/#HEAD/type/git_checkout_options
+ * https://github.com/libgit2/libgit2/blob/HEAD/include/git2/checkout.h#L251-295
+ */
+
+
+static int checkout_notify_cb(git_checkout_notify_t why,
+    const char *path, const git_diff_file *baseline,
+    const git_diff_file *target, const git_diff_file *workdir,
+    void *payload)
+{
+	bool *res = payload;
+
+	assert(why == GIT_CHECKOUT_NOTIFY_DIRTY);
+
+	*res = 1;
+	return 0;
+}
+
+
+bool git_repo_is_dirty(git_repository *repo)
+{
+	git_checkout_options opts;
+	bool res = 0;
+
+	/*
+	 * Initialization with GIT_CHECKOUT_OPTIONS_INIT complains about not
+	 * setting checkout_strategy. git_checkout_init_options is fine.
+	 */
+	git_checkout_init_options(&opts, GIT_CHECKOUT_OPTIONS_VERSION);
+	opts.checkout_strategy = GIT_CHECKOUT_NONE;
+		/* let's be explicit about this */
+	opts.notify_flags = GIT_CHECKOUT_NOTIFY_DIRTY;
+	opts.notify_cb = checkout_notify_cb;
+	opts.notify_payload = &res;
+	git_checkout_index(repo, NULL, &opts);
+
+	return res;
+}
+
+
+/*
+ * Git documentation says that git_libgit2_init can be called more then once
+ * but doesn't quite what happens then, e.g., whether references obtained
+ * before an init (except for the first, of course) can still be used after
+ * it. So we play it safe and initialize only once.
+ */
+
+void git_init_once(void)
+{
+	static bool initialized = 0;
+
+	if (!initialized) {
+		git_libgit2_init();
+		initialized = 1;
+	}
+}

eeshow/file/git-util.h

@@ -0,0 +1,24 @@
+/*
+ * file/git-util.h - Git utility functions
+ *
+ * Written 2016 by Werner Almesberger
+ * Copyright 2016 by Werner Almesberger
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ */
+
+#ifndef FILE_GIT_UTIL_H
+#define	FILE_GIT_UTIL_H
+
+#include <stdbool.h>
+
+#include <git2.h>
+
+
+bool git_repo_is_dirty(git_repository *repo);
+void git_init_once(void);
+
+#endif /* !FILE_GIT_UTIL_H */