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1 | git-bisect(1) |
2 | ============= | |
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3 | |
4 | NAME | |
5 | ---- | |
c3f0baac | 6 | git-bisect - Find the change that introduced a bug by binary search |
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7 | |
8 | ||
9 | SYNOPSIS | |
10 | -------- | |
a6080a0a | 11 | 'git bisect' <subcommand> <options> |
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12 | |
13 | DESCRIPTION | |
14 | ----------- | |
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15 | The command takes various subcommands, and different options depending |
16 | on the subcommand: | |
556cb4e5 | 17 | |
243a60fb | 18 | git bisect help |
6fe9c570 | 19 | git bisect start [<bad> [<good>...]] [--] [<paths>...] |
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20 | git bisect bad [<rev>] |
21 | git bisect good [<rev>...] | |
22 | git bisect skip [<rev>...] | |
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23 | git bisect reset [<branch>] |
24 | git bisect visualize | |
25 | git bisect replay <logfile> | |
26 | git bisect log | |
a17c4101 | 27 | git bisect run <cmd>... |
556cb4e5 | 28 | |
467c0197 | 29 | This command uses `git-rev-list --bisect` to help drive the |
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30 | binary search process to find which change introduced a bug, given an |
31 | old "good" commit object name and a later "bad" commit object name. | |
7fc9d69f | 32 | |
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33 | Getting help |
34 | ~~~~~~~~~~~~ | |
35 | ||
36 | Use "git bisect" to get a short usage description, and "git bisect | |
37 | help" or "git bisect -h" to get a long usage description. | |
38 | ||
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39 | Basic bisect commands: start, bad, good |
40 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
41 | ||
f85a4191 | 42 | The way you use it is: |
7fc9d69f | 43 | |
f85a4191 | 44 | ------------------------------------------------ |
556cb4e5 | 45 | $ git bisect start |
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46 | $ git bisect bad # Current version is bad |
47 | $ git bisect good v2.6.13-rc2 # v2.6.13-rc2 was the last version | |
48 | # tested that was good | |
f85a4191 | 49 | ------------------------------------------------ |
7fc9d69f | 50 | |
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51 | When you give at least one bad and one good versions, it will bisect |
52 | the revision tree and say something like: | |
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53 | |
54 | ------------------------------------------------ | |
55 | Bisecting: 675 revisions left to test after this | |
56 | ------------------------------------------------ | |
57 | ||
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58 | and check out the state in the middle. Now, compile that kernel, and |
59 | boot it. Now, let's say that this booted kernel works fine, then just | |
60 | do | |
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61 | |
62 | ------------------------------------------------ | |
556cb4e5 | 63 | $ git bisect good # this one is good |
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64 | ------------------------------------------------ |
65 | ||
66 | which will now say | |
67 | ||
68 | ------------------------------------------------ | |
69 | Bisecting: 337 revisions left to test after this | |
70 | ------------------------------------------------ | |
71 | ||
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72 | and you continue along, compiling that one, testing it, and depending |
73 | on whether it is good or bad, you say "git bisect good" or "git bisect | |
74 | bad", and ask for the next bisection. | |
f85a4191 | 75 | |
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76 | Until you have no more left, and you'll have been left with the first |
77 | bad kernel rev in "refs/bisect/bad". | |
f85a4191 | 78 | |
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79 | Bisect reset |
80 | ~~~~~~~~~~~~ | |
81 | ||
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82 | Oh, and then after you want to reset to the original head, do a |
83 | ||
84 | ------------------------------------------------ | |
556cb4e5 | 85 | $ git bisect reset |
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86 | ------------------------------------------------ |
87 | ||
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88 | to get back to the original branch, instead of being on the bisection |
89 | commit ("git bisect start" will do that for you too, actually: it will | |
90 | reset the bisection state). | |
7fc9d69f | 91 | |
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92 | Bisect visualize |
93 | ~~~~~~~~~~~~~~~~ | |
94 | ||
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95 | During the bisection process, you can say |
96 | ||
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97 | ------------ |
98 | $ git bisect visualize | |
99 | ------------ | |
8db9307c | 100 | |
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101 | to see the currently remaining suspects in `gitk`. `visualize` is a bit |
102 | too long to type and `view` is provided as a synonym. | |
103 | ||
467c0197 | 104 | If 'DISPLAY' environment variable is not set, `git-log` is used |
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105 | instead. You can even give command line options such as `-p` and |
106 | `--stat`. | |
107 | ||
108 | ------------ | |
109 | $ git bisect view --stat | |
110 | ------------ | |
8db9307c | 111 | |
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112 | Bisect log and bisect replay |
113 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
114 | ||
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115 | The good/bad input is logged, and |
116 | ||
117 | ------------ | |
118 | $ git bisect log | |
119 | ------------ | |
120 | ||
121 | shows what you have done so far. You can truncate its output somewhere | |
122 | and save it in a file, and run | |
b595ed14 | 123 | |
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124 | ------------ |
125 | $ git bisect replay that-file | |
126 | ------------ | |
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127 | |
128 | if you find later you made a mistake telling good/bad about a | |
129 | revision. | |
130 | ||
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131 | Avoiding to test a commit |
132 | ~~~~~~~~~~~~~~~~~~~~~~~~~ | |
133 | ||
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134 | If in a middle of bisect session, you know what the bisect suggested |
135 | to try next is not a good one to test (e.g. the change the commit | |
136 | introduces is known not to work in your environment and you know it | |
137 | does not have anything to do with the bug you are chasing), you may | |
138 | want to find a near-by commit and try that instead. | |
139 | ||
140 | It goes something like this: | |
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141 | |
142 | ------------ | |
143 | $ git bisect good/bad # previous round was good/bad. | |
144 | Bisecting: 337 revisions left to test after this | |
145 | $ git bisect visualize # oops, that is uninteresting. | |
146 | $ git reset --hard HEAD~3 # try 3 revs before what | |
147 | # was suggested | |
148 | ------------ | |
149 | ||
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150 | Then compile and test the one you chose to try. After that, tell |
151 | bisect what the result was as usual. | |
556cb4e5 | 152 | |
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153 | Bisect skip |
154 | ~~~~~~~~~~~~ | |
155 | ||
156 | Instead of choosing by yourself a nearby commit, you may just want git | |
157 | to do it for you using: | |
158 | ||
159 | ------------ | |
160 | $ git bisect skip # Current version cannot be tested | |
161 | ------------ | |
162 | ||
163 | But computing the commit to test may be slower afterwards and git may | |
164 | eventually not be able to tell the first bad among a bad and one or | |
165 | more "skip"ped commits. | |
166 | ||
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167 | Cutting down bisection by giving more parameters to bisect start |
168 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
1207f9e7 | 169 | |
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170 | You can further cut down the number of trials if you know what part of |
171 | the tree is involved in the problem you are tracking down, by giving | |
172 | paths parameters when you say `bisect start`, like this: | |
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173 | |
174 | ------------ | |
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175 | $ git bisect start -- arch/i386 include/asm-i386 |
176 | ------------ | |
177 | ||
178 | If you know beforehand more than one good commits, you can narrow the | |
179 | bisect space down without doing the whole tree checkout every time you | |
180 | give good commits. You give the bad revision immediately after `start` | |
181 | and then you give all the good revisions you have: | |
182 | ||
183 | ------------ | |
184 | $ git bisect start v2.6.20-rc6 v2.6.20-rc4 v2.6.20-rc1 -- | |
185 | # v2.6.20-rc6 is bad | |
186 | # v2.6.20-rc4 and v2.6.20-rc1 are good | |
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187 | ------------ |
188 | ||
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189 | Bisect run |
190 | ~~~~~~~~~~ | |
191 | ||
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192 | If you have a script that can tell if the current source code is good |
193 | or bad, you can automatically bisect using: | |
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194 | |
195 | ------------ | |
196 | $ git bisect run my_script | |
197 | ------------ | |
198 | ||
7891a281 | 199 | Note that the "run" script (`my_script` in the above example) should |
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200 | exit with code 0 in case the current source code is good. Exit with a |
201 | code between 1 and 127 (inclusive), except 125, if the current | |
202 | source code is bad. | |
a17c4101 | 203 | |
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204 | Any other exit code will abort the automatic bisect process. (A |
205 | program that does "exit(-1)" leaves $? = 255, see exit(3) manual page, | |
206 | the value is chopped with "& 0377".) | |
a17c4101 | 207 | |
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208 | The special exit code 125 should be used when the current source code |
209 | cannot be tested. If the "run" script exits with this code, the current | |
210 | revision will be skipped, see `git bisect skip` above. | |
211 | ||
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212 | You may often find that during bisect you want to have near-constant |
213 | tweaks (e.g., s/#define DEBUG 0/#define DEBUG 1/ in a header file, or | |
214 | "revision that does not have this commit needs this patch applied to | |
215 | work around other problem this bisection is not interested in") | |
216 | applied to the revision being tested. | |
217 | ||
483bc4f0 | 218 | To cope with such a situation, after the inner `git-bisect` finds the |
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219 | next revision to test, with the "run" script, you can apply that tweak |
220 | before compiling, run the real test, and after the test decides if the | |
221 | revision (possibly with the needed tweaks) passed the test, rewind the | |
222 | tree to the pristine state. Finally the "run" script can exit with | |
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223 | the status of the real test to let the "git bisect run" command loop to |
224 | determine the outcome. | |
7fc9d69f | 225 | |
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226 | EXAMPLES |
227 | -------- | |
228 | ||
229 | * Automatically bisect a broken build between v1.2 and HEAD: | |
230 | + | |
231 | ------------ | |
232 | $ git bisect start HEAD v1.2 -- # HEAD is bad, v1.2 is good | |
233 | $ git bisect run make # "make" builds the app | |
234 | ------------ | |
235 | ||
236 | * Automatically bisect a broken test suite: | |
237 | + | |
238 | ------------ | |
239 | $ cat ~/test.sh | |
240 | #!/bin/sh | |
241 | make || exit 125 # this "skip"s broken builds | |
242 | make test # "make test" runs the test suite | |
243 | $ git bisect start v1.3 v1.1 -- # v1.3 is bad, v1.1 is good | |
244 | $ git bisect run ~/test.sh | |
245 | ------------ | |
246 | + | |
247 | Here we use a "test.sh" custom script. In this script, if "make" | |
248 | fails, we "skip" the current commit. | |
249 | + | |
250 | It's safer to use a custom script outside the repo to prevent | |
251 | interactions between the bisect, make and test processes and the | |
252 | script. | |
253 | + | |
254 | And "make test" should "exit 0", if the test suite passes, and | |
255 | "exit 1" (for example) otherwise. | |
256 | ||
257 | * Automatically bisect a broken test case: | |
258 | + | |
259 | ------------ | |
260 | $ cat ~/test.sh | |
261 | #!/bin/sh | |
262 | make || exit 125 # this "skip"s broken builds | |
263 | ~/check_test_case.sh # does the test case passes ? | |
264 | $ git bisect start HEAD HEAD~10 -- # culprit is among the last 10 | |
265 | $ git bisect run ~/test.sh | |
266 | ------------ | |
267 | + | |
268 | Here "check_test_case.sh" should "exit 0", if the test case passes, | |
269 | and "exit 1" (for example) otherwise. | |
270 | + | |
271 | It's safer if both "test.sh" and "check_test_case.sh" scripts are | |
272 | outside the repo to prevent interactions between the bisect, make and | |
273 | test processes and the scripts. | |
274 | ||
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275 | Author |
276 | ------ | |
277 | Written by Linus Torvalds <torvalds@osdl.org> | |
278 | ||
279 | Documentation | |
df8baa42 | 280 | ------------- |
7fc9d69f JH |
281 | Documentation by Junio C Hamano and the git-list <git@vger.kernel.org>. |
282 | ||
283 | GIT | |
284 | --- | |
9e1f0a85 | 285 | Part of the linkgit:git[1] suite |