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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 | |
6fe9c570 | 18 | git bisect start [<bad> [<good>...]] [--] [<paths>...] |
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19 | git bisect bad [<rev>] |
20 | git bisect good [<rev>...] | |
21 | git bisect skip [<rev>...] | |
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22 | git bisect reset [<branch>] |
23 | git bisect visualize | |
24 | git bisect replay <logfile> | |
25 | git bisect log | |
a17c4101 | 26 | git bisect run <cmd>... |
556cb4e5 | 27 | |
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28 | This command uses 'git-rev-list --bisect' option to help drive the |
29 | binary search process to find which change introduced a bug, given an | |
30 | old "good" commit object name and a later "bad" commit object name. | |
7fc9d69f | 31 | |
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32 | Basic bisect commands: start, bad, good |
33 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
34 | ||
f85a4191 | 35 | The way you use it is: |
7fc9d69f | 36 | |
f85a4191 | 37 | ------------------------------------------------ |
556cb4e5 | 38 | $ git bisect start |
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39 | $ git bisect bad # Current version is bad |
40 | $ git bisect good v2.6.13-rc2 # v2.6.13-rc2 was the last version | |
41 | # tested that was good | |
f85a4191 | 42 | ------------------------------------------------ |
7fc9d69f | 43 | |
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44 | When you give at least one bad and one good versions, it will bisect |
45 | the revision tree and say something like: | |
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46 | |
47 | ------------------------------------------------ | |
48 | Bisecting: 675 revisions left to test after this | |
49 | ------------------------------------------------ | |
50 | ||
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51 | and check out the state in the middle. Now, compile that kernel, and |
52 | boot it. Now, let's say that this booted kernel works fine, then just | |
53 | do | |
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54 | |
55 | ------------------------------------------------ | |
556cb4e5 | 56 | $ git bisect good # this one is good |
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57 | ------------------------------------------------ |
58 | ||
59 | which will now say | |
60 | ||
61 | ------------------------------------------------ | |
62 | Bisecting: 337 revisions left to test after this | |
63 | ------------------------------------------------ | |
64 | ||
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65 | and you continue along, compiling that one, testing it, and depending |
66 | on whether it is good or bad, you say "git bisect good" or "git bisect | |
67 | bad", and ask for the next bisection. | |
f85a4191 | 68 | |
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69 | Until you have no more left, and you'll have been left with the first |
70 | bad kernel rev in "refs/bisect/bad". | |
f85a4191 | 71 | |
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72 | Bisect reset |
73 | ~~~~~~~~~~~~ | |
74 | ||
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75 | Oh, and then after you want to reset to the original head, do a |
76 | ||
77 | ------------------------------------------------ | |
556cb4e5 | 78 | $ git bisect reset |
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79 | ------------------------------------------------ |
80 | ||
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81 | to get back to the master branch, instead of being in one of the |
82 | bisection branches ("git bisect start" will do that for you too, | |
83 | actually: it will reset the bisection state, and before it does that | |
84 | it checks that you're not using some old bisection branch). | |
7fc9d69f | 85 | |
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86 | Bisect visualize |
87 | ~~~~~~~~~~~~~~~~ | |
88 | ||
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89 | During the bisection process, you can say |
90 | ||
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91 | ------------ |
92 | $ git bisect visualize | |
93 | ------------ | |
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94 | |
95 | to see the currently remaining suspects in `gitk`. | |
96 | ||
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97 | Bisect log and bisect replay |
98 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
99 | ||
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100 | The good/bad input is logged, and |
101 | ||
102 | ------------ | |
103 | $ git bisect log | |
104 | ------------ | |
105 | ||
106 | shows what you have done so far. You can truncate its output somewhere | |
107 | and save it in a file, and run | |
b595ed14 | 108 | |
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109 | ------------ |
110 | $ git bisect replay that-file | |
111 | ------------ | |
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112 | |
113 | if you find later you made a mistake telling good/bad about a | |
114 | revision. | |
115 | ||
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116 | Avoiding to test a commit |
117 | ~~~~~~~~~~~~~~~~~~~~~~~~~ | |
118 | ||
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119 | If in a middle of bisect session, you know what the bisect suggested |
120 | to try next is not a good one to test (e.g. the change the commit | |
121 | introduces is known not to work in your environment and you know it | |
122 | does not have anything to do with the bug you are chasing), you may | |
123 | want to find a near-by commit and try that instead. | |
124 | ||
125 | It goes something like this: | |
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126 | |
127 | ------------ | |
128 | $ git bisect good/bad # previous round was good/bad. | |
129 | Bisecting: 337 revisions left to test after this | |
130 | $ git bisect visualize # oops, that is uninteresting. | |
131 | $ git reset --hard HEAD~3 # try 3 revs before what | |
132 | # was suggested | |
133 | ------------ | |
134 | ||
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135 | Then compile and test the one you chose to try. After that, tell |
136 | bisect what the result was as usual. | |
556cb4e5 | 137 | |
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138 | Bisect skip |
139 | ~~~~~~~~~~~~ | |
140 | ||
141 | Instead of choosing by yourself a nearby commit, you may just want git | |
142 | to do it for you using: | |
143 | ||
144 | ------------ | |
145 | $ git bisect skip # Current version cannot be tested | |
146 | ------------ | |
147 | ||
148 | But computing the commit to test may be slower afterwards and git may | |
149 | eventually not be able to tell the first bad among a bad and one or | |
150 | more "skip"ped commits. | |
151 | ||
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152 | Cutting down bisection by giving more parameters to bisect start |
153 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
1207f9e7 | 154 | |
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155 | You can further cut down the number of trials if you know what part of |
156 | the tree is involved in the problem you are tracking down, by giving | |
157 | paths parameters when you say `bisect start`, like this: | |
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158 | |
159 | ------------ | |
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160 | $ git bisect start -- arch/i386 include/asm-i386 |
161 | ------------ | |
162 | ||
163 | If you know beforehand more than one good commits, you can narrow the | |
164 | bisect space down without doing the whole tree checkout every time you | |
165 | give good commits. You give the bad revision immediately after `start` | |
166 | and then you give all the good revisions you have: | |
167 | ||
168 | ------------ | |
169 | $ git bisect start v2.6.20-rc6 v2.6.20-rc4 v2.6.20-rc1 -- | |
170 | # v2.6.20-rc6 is bad | |
171 | # v2.6.20-rc4 and v2.6.20-rc1 are good | |
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172 | ------------ |
173 | ||
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174 | Bisect run |
175 | ~~~~~~~~~~ | |
176 | ||
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177 | If you have a script that can tell if the current source code is good |
178 | or bad, you can automatically bisect using: | |
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179 | |
180 | ------------ | |
181 | $ git bisect run my_script | |
182 | ------------ | |
183 | ||
7891a281 | 184 | Note that the "run" script (`my_script` in the above example) should |
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185 | exit with code 0 in case the current source code is good. Exit with a |
186 | code between 1 and 127 (inclusive), except 125, if the current | |
187 | source code is bad. | |
a17c4101 | 188 | |
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189 | Any other exit code will abort the automatic bisect process. (A |
190 | program that does "exit(-1)" leaves $? = 255, see exit(3) manual page, | |
191 | the value is chopped with "& 0377".) | |
a17c4101 | 192 | |
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193 | The special exit code 125 should be used when the current source code |
194 | cannot be tested. If the "run" script exits with this code, the current | |
195 | revision will be skipped, see `git bisect skip` above. | |
196 | ||
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197 | You may often find that during bisect you want to have near-constant |
198 | tweaks (e.g., s/#define DEBUG 0/#define DEBUG 1/ in a header file, or | |
199 | "revision that does not have this commit needs this patch applied to | |
200 | work around other problem this bisection is not interested in") | |
201 | applied to the revision being tested. | |
202 | ||
203 | To cope with such a situation, after the inner git-bisect finds the | |
204 | next revision to test, with the "run" script, you can apply that tweak | |
205 | before compiling, run the real test, and after the test decides if the | |
206 | revision (possibly with the needed tweaks) passed the test, rewind the | |
207 | tree to the pristine state. Finally the "run" script can exit with | |
208 | the status of the real test to let "git bisect run" command loop to | |
209 | know the outcome. | |
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210 | |
211 | Author | |
212 | ------ | |
213 | Written by Linus Torvalds <torvalds@osdl.org> | |
214 | ||
215 | Documentation | |
df8baa42 | 216 | ------------- |
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217 | Documentation by Junio C Hamano and the git-list <git@vger.kernel.org>. |
218 | ||
219 | GIT | |
220 | --- | |
a7154e91 | 221 | Part of the gitlink:git[7] suite |