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git wrapper: DWIM mistyped commands

This patch introduces a modified Damerau-Levenshtein algorithm into
Git's code base, and uses it with the following penalties to show some
similar commands when an unknown command was encountered:

	swap = 0, insertion = 1, substitution = 2, deletion = 4

A typical output would now look like this:

	$ git sm
	git: 'sm' is not a git-command. See 'git --help'.

	Did you mean one of these?
		am
		rm

The cut-off is at similarity rating 6, which was empirically determined
to give sensible results.

As a convenience, if there is only one candidate, Git continues under
the assumption that the user mistyped it.  Example:

	$ git reabse
	WARNING: You called a Git program named 'reabse', which does
	not exist.
	Continuing under the assumption that you meant 'rebase'
	[...]

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Alex Riesen <raa.lkml@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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commit 8af84dadb142f7321ff0ce8690385e99da8ede2f 1 parent a1184d8
@dscho dscho authored gitster committed
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2  Makefile
@@ -358,6 +358,7 @@ LIB_H += graph.h
LIB_H += grep.h
LIB_H += hash.h
LIB_H += help.h
+LIB_H += levenshtein.h
LIB_H += list-objects.h
LIB_H += ll-merge.h
LIB_H += log-tree.h
@@ -433,6 +434,7 @@ LIB_OBJS += hash.o
LIB_OBJS += help.o
LIB_OBJS += ident.o
LIB_OBJS += interpolate.o
+LIB_OBJS += levenshtein.o
LIB_OBJS += list-objects.o
LIB_OBJS += ll-merge.o
LIB_OBJS += lockfile.o
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2  builtin.h
@@ -11,7 +11,7 @@ extern const char git_usage_string[];
extern const char git_more_info_string[];
extern void list_common_cmds_help(void);
-extern void help_unknown_cmd(const char *cmd);
+extern const char *help_unknown_cmd(const char *cmd);
extern void prune_packed_objects(int);
extern int read_line_with_nul(char *buf, int size, FILE *file);
extern int fmt_merge_msg(int merge_summary, struct strbuf *in,
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4 git.c
@@ -499,7 +499,9 @@ int main(int argc, const char **argv)
cmd, argv[0]);
exit(1);
}
- help_unknown_cmd(cmd);
+ argv[0] = help_unknown_cmd(cmd);
+ handle_internal_command(argc, argv);
+ execv_dashed_external(argv);
}
fprintf(stderr, "Failed to run command '%s': %s\n",
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72 help.c
@@ -1,6 +1,7 @@
#include "cache.h"
#include "builtin.h"
#include "exec_cmd.h"
+#include "levenshtein.h"
#include "help.h"
/* most GUI terminals set COLUMNS (although some don't export it) */
@@ -37,6 +38,16 @@ void add_cmdname(struct cmdnames *cmds, const char *name, int len)
cmds->names[cmds->cnt++] = ent;
}
+static void clean_cmdnames(struct cmdnames *cmds)
+{
+ int i;
+ for (i = 0; i < cmds->cnt; ++i)
+ free(cmds->names[i]);
+ free(cmds->names);
+ cmds->cnt = 0;
+ cmds->alloc = 0;
+}
+
static int cmdname_compare(const void *a_, const void *b_)
{
struct cmdname *a = *(struct cmdname **)a_;
@@ -257,9 +268,68 @@ int is_in_cmdlist(struct cmdnames *c, const char *s)
return 0;
}
-void help_unknown_cmd(const char *cmd)
+static int levenshtein_compare(const void *p1, const void *p2)
+{
+ const struct cmdname *const *c1 = p1, *const *c2 = p2;
+ const char *s1 = (*c1)->name, *s2 = (*c2)->name;
+ int l1 = (*c1)->len;
+ int l2 = (*c2)->len;
+ return l1 != l2 ? l1 - l2 : strcmp(s1, s2);
+}
+
+const char *help_unknown_cmd(const char *cmd)
{
+ int i, n, best_similarity = 0;
+ struct cmdnames main_cmds, other_cmds;
+
+ memset(&main_cmds, 0, sizeof(main_cmds));
+ memset(&other_cmds, 0, sizeof(main_cmds));
+
+ load_command_list("git-", &main_cmds, &other_cmds);
+
+ ALLOC_GROW(main_cmds.names, main_cmds.cnt + other_cmds.cnt,
+ main_cmds.alloc);
+ memcpy(main_cmds.names + main_cmds.cnt, other_cmds.names,
+ other_cmds.cnt * sizeof(other_cmds.names[0]));
+ main_cmds.cnt += other_cmds.cnt;
+ free(other_cmds.names);
+
+ /* This reuses cmdname->len for similarity index */
+ for (i = 0; i < main_cmds.cnt; ++i)
+ main_cmds.names[i]->len =
+ levenshtein(cmd, main_cmds.names[i]->name, 0, 2, 1, 4);
+
+ qsort(main_cmds.names, main_cmds.cnt,
+ sizeof(*main_cmds.names), levenshtein_compare);
+
+ if (!main_cmds.cnt)
+ die ("Uh oh. Your system reports no Git commands at all.");
+
+ best_similarity = main_cmds.names[0]->len;
+ n = 1;
+ while (n < main_cmds.cnt && best_similarity == main_cmds.names[n]->len)
+ ++n;
+ if (n == 1) {
+ const char *assumed = main_cmds.names[0]->name;
+ main_cmds.names[0] = NULL;
+ clean_cmdnames(&main_cmds);
+ fprintf(stderr, "WARNING: You called a Git program named '%s', "
+ "which does not exist.\n"
+ "Continuing under the assumption that you meant '%s'\n",
+ cmd, assumed);
+ return assumed;
+ }
+
fprintf(stderr, "git: '%s' is not a git-command. See 'git --help'.\n", cmd);
+
+ if (best_similarity < 6) {
+ fprintf(stderr, "\nDid you mean %s?\n",
+ n < 2 ? "this": "one of these");
+
+ for (i = 0; i < n; i++)
+ fprintf(stderr, "\t%s\n", main_cmds.names[i]->name);
+ }
+
exit(1);
}
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2  help.h
@@ -5,7 +5,7 @@ struct cmdnames {
int alloc;
int cnt;
struct cmdname {
- size_t len;
+ size_t len; /* also used for similarity index in help.c */
char name[FLEX_ARRAY];
} **names;
};
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47 levenshtein.c
@@ -0,0 +1,47 @@
+#include "cache.h"
+#include "levenshtein.h"
+
+int levenshtein(const char *string1, const char *string2,
+ int w, int s, int a, int d)
+{
+ int len1 = strlen(string1), len2 = strlen(string2);
+ int *row0 = xmalloc(sizeof(int) * (len2 + 1));
+ int *row1 = xmalloc(sizeof(int) * (len2 + 1));
+ int *row2 = xmalloc(sizeof(int) * (len2 + 1));
+ int i, j;
+
+ for (j = 0; j <= len2; j++)
+ row1[j] = j * a;
+ for (i = 0; i < len1; i++) {
+ int *dummy;
+
+ row2[0] = (i + 1) * d;
+ for (j = 0; j < len2; j++) {
+ /* substitution */
+ row2[j + 1] = row1[j] + s * (string1[i] != string2[j]);
+ /* swap */
+ if (i > 0 && j > 0 && string1[i - 1] == string2[j] &&
+ string1[i] == string2[j - 1] &&
+ row2[j + 1] > row0[j - 1] + w)
+ row2[j + 1] = row0[j - 1] + w;
+ /* deletion */
+ if (j + 1 < len2 && row2[j + 1] > row1[j + 1] + d)
+ row2[j + 1] = row1[j + 1] + d;
+ /* insertion */
+ if (row2[j + 1] > row2[j] + a)
+ row2[j + 1] = row2[j] + a;
+ }
+
+ dummy = row0;
+ row0 = row1;
+ row1 = row2;
+ row2 = dummy;
+ }
+
+ i = row1[len2];
+ free(row0);
+ free(row1);
+ free(row2);
+
+ return i;
+}
View
8 levenshtein.h
@@ -0,0 +1,8 @@
+#ifndef LEVENSHTEIN_H
+#define LEVENSHTEIN_H
+
+int levenshtein(const char *string1, const char *string2,
+ int swap_penalty, int substition_penalty,
+ int insertion_penalty, int deletion_penalty);
+
+#endif
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