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range-diff: support reading mbox files
Internally, the `git range-diff` command spawns a `git log` process and parses its output for the given commit ranges. This works well when the patches that need to be compared are present in the local repository in the form of commits. In scenarios where that is not the case, the `range-diff` command is currently less helpful. The Git mailing list is such a scenario: Instead of using Git to exchange commits, the patches are sent there as plain-text and no commit range can be specified to let `range-diff` consume those patches. Instead, the expectation is to download the mails, apply them locally and then use `range-diff`. This can be quite cumbersome e.g. when a suitable base revision has to be found first where the patch applies cleanly. Let's offer a way to read those patches from pre-prepared MBox files instead when an argument "mbox:<filename>" is passed instead of a commit range. For extra convenience, interpret the filename `-` as standard input. This makes it easy to compare contributions on the mailing list with the actual commits that were integrated into Git's main branch. Example: commit=5c4003ca3f0e9ac6d3c8aa3e387ff843bd440411 mid=bdfa3845b81531863941e6a97c28eb1afa62dd2c.1489435755.git.johannes.schindelin@gmx.de curl -s https://lore.kernel.org/git/$mid/raw | git range-diff mbox:- $commit^! This addresses gitgitgadget#207 Signed-off-by: Johannes Schindelin <[email protected]>
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‎Documentation/git-range-diff.txt

Lines changed: 2 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -37,7 +37,8 @@ There are three ways to specify the commit ranges:
3737

3838
- `<range1> <range2>`: Either commit range can be of the form
3939
`<base>..<rev>`, `<rev>^!` or `<rev>^-<n>`. See `SPECIFYING RANGES`
40-
in linkgit:gitrevisions[7] for more details.
40+
in linkgit:gitrevisions[7] for more details. Alternatively, the
41+
patches can be provided as an mbox-formatted file via `mbox:<path>`.
4142

4243
- `<rev1>...<rev2>`. This is equivalent to
4344
`<rev2>..<rev1> <rev1>..<rev2>`.

‎range-diff.c

Lines changed: 332 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -12,6 +12,7 @@
1212
#include "userdiff.h"
1313
#include "apply.h"
1414
#include "revision.h"
15+
#include "dir.h"
1516

1617
struct patch_util {
1718
/* For the search for an exact match */
@@ -26,6 +27,309 @@ struct patch_util {
2627
struct object_id oid;
2728
};
2829

30+
static inline int strtost(char const *s, size_t *result, const char **end)
31+
{
32+
unsigned long u;
33+
char *p;
34+
35+
errno = 0;
36+
/* negative values would be accepted by strtoul */
37+
if (!isdigit(*s))
38+
return -1;
39+
u = strtoul(s, &p, 10);
40+
if (errno || p == s)
41+
return -1;
42+
if (result)
43+
*result = u;
44+
*end = p;
45+
46+
return 0;
47+
}
48+
49+
static int parse_hunk_header(const char *p,
50+
size_t *old_count, size_t *new_count,
51+
const char **end)
52+
{
53+
size_t o = 1, n = 1;
54+
55+
if (!skip_prefix(p, "@@ -", &p) ||
56+
strtost(p, NULL, &p) ||
57+
/* The range is -<start>[,<count>], defaulting to count = 1 */
58+
!(*p == ' ' || (*p == ',' && !strtost(p + 1, &o, &p))) ||
59+
!skip_prefix(p, " +", &p) ||
60+
strtost(p, NULL, &p) ||
61+
/* The range is +<start>[,<count>], defaulting to count = 1 */
62+
!(*p == ' ' || (*p == ',' && !strtost(p + 1, &n, &p))) ||
63+
!skip_prefix(p, " @@", &p))
64+
return -1;
65+
66+
*old_count = o;
67+
*new_count = n;
68+
*end = p;
69+
70+
return 0;
71+
}
72+
73+
/*
74+
* This function finds the end of the line, replaces the newline character with
75+
* a NUL, and returns the offset of the start of the next line.
76+
*
77+
* If no newline character was found, it returns the offset of the trailing NUL
78+
* instead.
79+
*/
80+
static inline int find_next_line(const char *line, size_t size)
81+
{
82+
char *eol;
83+
84+
eol = memchr(line, '\n', size);
85+
if (!eol)
86+
return size;
87+
88+
*eol = '\0';
89+
90+
return eol + 1 - line;
91+
}
92+
93+
static int read_mbox(const char *path, struct string_list *list)
94+
{
95+
struct strbuf buf = STRBUF_INIT, contents = STRBUF_INIT;
96+
struct strbuf long_subject = STRBUF_INIT;
97+
struct patch_util *util = NULL;
98+
enum {
99+
MBOX_BEFORE_HEADER,
100+
MBOX_IN_HEADER,
101+
MBOX_IN_COMMIT_MESSAGE,
102+
MBOX_AFTER_TRIPLE_DASH,
103+
MBOX_IN_DIFF
104+
} state = MBOX_BEFORE_HEADER;
105+
char *line, *current_filename = NULL;
106+
int len;
107+
size_t size, old_count = 0, new_count = 0;
108+
const char *author = NULL, *subject = NULL;
109+
110+
if (!strcmp(path, "-")) {
111+
if (strbuf_read(&contents, STDIN_FILENO, 0) < 0)
112+
return error_errno(_("could not read stdin"));
113+
} else if (strbuf_read_file(&contents, path, 0) < 0)
114+
return error_errno(_("could not read '%s'"), path);
115+
116+
line = contents.buf;
117+
size = contents.len;
118+
for (; size; size -= len, line += len) {
119+
const char *p;
120+
121+
len = find_next_line(line, size);
122+
123+
if (state == MBOX_BEFORE_HEADER ||
124+
(state == MBOX_IN_DIFF && line[0] == 'F')) {
125+
if (!skip_prefix(line, "From ", &p))
126+
continue;
127+
128+
util = xcalloc(1, sizeof(*util));
129+
if (get_oid_hex(p, &util->oid) < 0)
130+
oidcpy(&util->oid, null_oid());
131+
util->matching = -1;
132+
author = subject = NULL;
133+
134+
state = MBOX_IN_HEADER;
135+
continue;
136+
}
137+
138+
if (starts_with(line, "diff --git ")) {
139+
struct patch patch = { 0 };
140+
struct strbuf root = STRBUF_INIT;
141+
int linenr = 0;
142+
int orig_len;
143+
144+
state = MBOX_IN_DIFF;
145+
old_count = new_count = 0;
146+
strbuf_addch(&buf, '\n');
147+
if (!util->diff_offset)
148+
util->diff_offset = buf.len;
149+
150+
orig_len = len;
151+
/* `find_next_line()`'s replaced the LF with a NUL */
152+
line[len - 1] = '\n';
153+
len = len > 1 && line[len - 2] == '\r' ?
154+
error(_("cannot handle diff headers with "
155+
"CR/LF line endings")) :
156+
parse_git_diff_header(&root, &linenr, 1, line,
157+
len, size, &patch);
158+
if (len < 0) {
159+
error(_("could not parse git header '%.*s'"),
160+
orig_len, line);
161+
release_patch(&patch);
162+
free(util);
163+
free(current_filename);
164+
string_list_clear(list, 1);
165+
strbuf_release(&buf);
166+
strbuf_release(&contents);
167+
strbuf_release(&long_subject);
168+
return -1;
169+
}
170+
171+
if (patch.old_name)
172+
skip_prefix(patch.old_name, "a/",
173+
(const char **)&patch.old_name);
174+
if (patch.new_name)
175+
skip_prefix(patch.new_name, "b/",
176+
(const char **)&patch.new_name);
177+
178+
strbuf_addstr(&buf, " ## ");
179+
if (patch.is_new)
180+
strbuf_addf(&buf, "%s (new)", patch.new_name);
181+
else if (patch.is_delete)
182+
strbuf_addf(&buf, "%s (deleted)", patch.old_name);
183+
else if (patch.is_rename)
184+
strbuf_addf(&buf, "%s => %s", patch.old_name, patch.new_name);
185+
else
186+
strbuf_addstr(&buf, patch.new_name);
187+
188+
free(current_filename);
189+
if (patch.is_delete)
190+
current_filename = xstrdup(patch.old_name);
191+
else
192+
current_filename = xstrdup(patch.new_name);
193+
194+
if (patch.new_mode && patch.old_mode &&
195+
patch.old_mode != patch.new_mode)
196+
strbuf_addf(&buf, " (mode change %06o => %06o)",
197+
patch.old_mode, patch.new_mode);
198+
199+
strbuf_addstr(&buf, " ##\n");
200+
util->diffsize++;
201+
release_patch(&patch);
202+
} else if (state == MBOX_IN_HEADER) {
203+
if (!line[0]) {
204+
state = MBOX_IN_COMMIT_MESSAGE;
205+
/* Look for an in-body From: */
206+
if (skip_prefix(line + 1, "From: ", &p)) {
207+
size -= p - line;
208+
line += p - line;
209+
len = find_next_line(line, size);
210+
211+
while (isspace(*p))
212+
p++;
213+
author = p;
214+
}
215+
strbuf_addstr(&buf, " ## Metadata ##\n");
216+
if (author)
217+
strbuf_addf(&buf, "Author: %s\n", author);
218+
strbuf_addstr(&buf, "\n ## Commit message ##\n");
219+
if (subject)
220+
strbuf_addf(&buf, " %s\n\n", subject);
221+
} else if (skip_prefix(line, "From: ", &p)) {
222+
while (isspace(*p))
223+
p++;
224+
author = p;
225+
} else if (skip_prefix(line, "Subject: ", &p)) {
226+
const char *q;
227+
228+
while (isspace(*p))
229+
p++;
230+
subject = p;
231+
232+
if (starts_with(p, "[PATCH") &&
233+
(q = strchr(p, ']'))) {
234+
q++;
235+
while (isspace(*q))
236+
q++;
237+
subject = q;
238+
}
239+
240+
if (len < size && line[len] == ' ') {
241+
/* handle long subject */
242+
strbuf_reset(&long_subject);
243+
strbuf_addstr(&long_subject, subject);
244+
while (len < size && line[len] == ' ') {
245+
line += len;
246+
size -= len;
247+
len = find_next_line(line, size);
248+
strbuf_addstr(&long_subject, line);
249+
}
250+
subject = long_subject.buf;
251+
}
252+
}
253+
} else if (state == MBOX_IN_COMMIT_MESSAGE) {
254+
if (!line[0]) {
255+
strbuf_addch(&buf, '\n');
256+
} else if (strcmp(line, "---")) {
257+
int tabs = 0;
258+
259+
/* simulate tab expansion */
260+
while (line[tabs] == '\t')
261+
tabs++;
262+
strbuf_addf(&buf, "%*s%s\n",
263+
4 + 8 * tabs, "", line + tabs);
264+
} else {
265+
/*
266+
* Trim the trailing newline that is added
267+
* by `format-patch`.
268+
*/
269+
strbuf_trim_trailing_newline(&buf);
270+
state = MBOX_AFTER_TRIPLE_DASH;
271+
}
272+
} else if (state == MBOX_IN_DIFF) {
273+
switch (line[0]) {
274+
case '\0':
275+
continue; /* ignore empty lines after diff */
276+
case '+':
277+
case '-':
278+
case ' ':
279+
/* A `-- ` line indicates the end of a diff */
280+
if (!old_count && !new_count)
281+
break;
282+
if (old_count && line[0] != '+')
283+
old_count--;
284+
if (new_count && line[0] != '-')
285+
new_count--;
286+
/* fallthrough */
287+
case '\\':
288+
strbuf_addstr(&buf, line);
289+
strbuf_addch(&buf, '\n');
290+
util->diffsize++;
291+
continue;
292+
case '@':
293+
if (parse_hunk_header(line, &old_count,
294+
&new_count, &p))
295+
break;
296+
297+
strbuf_addstr(&buf, "@@");
298+
if (current_filename && *p)
299+
strbuf_addf(&buf, " %s:",
300+
current_filename);
301+
strbuf_addstr(&buf, p);
302+
strbuf_addch(&buf, '\n');
303+
util->diffsize++;
304+
continue;
305+
}
306+
307+
if (util) {
308+
string_list_append(list, buf.buf)->util = util;
309+
strbuf_reset(&buf);
310+
}
311+
util = xcalloc(1, sizeof(*util));
312+
oidcpy(&util->oid, null_oid());
313+
util->matching = -1;
314+
author = subject = NULL;
315+
state = MBOX_BEFORE_HEADER;
316+
}
317+
}
318+
strbuf_release(&contents);
319+
320+
if (util) {
321+
if (state == MBOX_IN_DIFF)
322+
string_list_append(list, buf.buf)->util = util;
323+
else
324+
free(util);
325+
}
326+
strbuf_release(&buf);
327+
strbuf_release(&long_subject);
328+
free(current_filename);
329+
330+
return 0;
331+
}
332+
29333
/*
30334
* Reads the patches into a string list, with the `util` field being populated
31335
* as struct object_id (will need to be free()d).
@@ -41,6 +345,10 @@ static int read_patches(const char *range, struct string_list *list,
41345
ssize_t len;
42346
size_t size;
43347
int ret = -1;
348+
const char *path;
349+
350+
if (skip_prefix(range, "mbox:", &path))
351+
return read_mbox(path, list);
44352

45353
strvec_pushl(&cp.args, "log", "--no-color", "-p", "--no-merges",
46354
"--reverse", "--date-order", "--decorate=no",
@@ -424,6 +732,19 @@ static void output_pair_header(struct diff_options *diffopt,
424732

425733
strbuf_addch(buf, ' ');
426734
pp_commit_easy(CMIT_FMT_ONELINE, commit, buf);
735+
} else {
736+
struct patch_util *util = b_util ? b_util : a_util;
737+
const char *needle = "\n ## Commit message ##\n";
738+
const char *p = !util || !util->patch ?
739+
NULL : strstr(util->patch, needle);
740+
if (p) {
741+
if (status == '!')
742+
strbuf_addf(buf, "%s%s", color_reset, color);
743+
744+
strbuf_addch(buf, ' ');
745+
p += strlen(needle);
746+
strbuf_add(buf, p, strchrnul(p, '\n') - p);
747+
}
427748
}
428749
strbuf_addf(buf, "%s\n", color_reset);
429750

@@ -554,6 +875,9 @@ int show_range_diff(const char *range1, const char *range2,
554875
if (range_diff_opts->left_only && range_diff_opts->right_only)
555876
res = error(_("options '%s' and '%s' cannot be used together"), "--left-only", "--right-only");
556877

878+
if (!strcmp(range1, "mbox:-") && !strcmp(range2, "mbox:-"))
879+
res = error(_("only one mbox can be read from stdin"));
880+
557881
if (!res && read_patches(range1, &branch1, range_diff_opts->other_arg))
558882
res = error(_("could not parse log for '%s'"), range1);
559883
if (!res && read_patches(range2, &branch2, range_diff_opts->other_arg))
@@ -575,10 +899,17 @@ int show_range_diff(const char *range1, const char *range2,
575899
int is_range_diff_range(const char *arg)
576900
{
577901
char *copy = xstrdup(arg); /* setup_revisions() modifies it */
578-
const char *argv[] = { "", copy, "--", NULL };
902+
const char *argv[] = { "", copy, "--", NULL }, *path;
579903
int i, positive = 0, negative = 0;
580904
struct rev_info revs;
581905

906+
if (skip_prefix(arg, "mbox:", &path)) {
907+
if (!strcmp(path, "-") || file_exists(path))
908+
return 1;
909+
error_errno(_("not an mbox: '%s'"), path);
910+
return 0;
911+
}
912+
582913
init_revisions(&revs, NULL);
583914
if (setup_revisions(3, argv, &revs, NULL) == 1) {
584915
for (i = 0; i < revs.pending.nr; i++)

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