git update-ref [-m <reason>] (-d <ref> [<oldvalue>] | [--no-deref] <ref> <newvalue> [<oldvalue>])
git update-ref HEAD "$head"
echo "$head" > "$GIT_DIR/HEAD"
SetEnv GIT_PROJECT_ROOT /path/to/repo
SetEnv GIT_HTTP_EXPORT_ALL
ScriptAlias /git/ /usr/lib/git-core/git-http-backend/
<LocationMatch "^/git/.*/git-receive-pack$">
AuthType Basic
AuthName "Git Access"
Require group committers
...
</LocationMatch>
git update-index --assume-unchanged -- path/to/file # 启用忽略 git update-index --no-assume-unchanged -- path/to/file # 停用忽略
77 gewang@LM-SHC-00355679@13:15:19:~/test/123
=> git diff
diff --git a/f b/f
index 541d3ff..847939a 100644
--- a/f
+++ b/f
@@ -5,3 +5,4 @@ abcaaa
aaa
dfadfaa
dlfaldf
+#####
78 gewang@LM-SHC-00355679@13:15:22:~/test/123
=> git update-index --assume-unchanged f
79 gewang@LM-SHC-00355679@13:15:36:~/test/123
=> git diff
80 gewang@LM-SHC-00355679@13:15:39:~/test/123
=> git status -s
81 gewang@LM-SHC-00355679@13:15:43:~/test/123
=> echo '-------' >> f
82 gewang@LM-SHC-00355679@13:16:04:~/test/123
=> git diff f
83 gewang@LM-SHC-00355679@13:16:06:~/test/123
=> git status -s
84 gewang@LM-SHC-00355679@13:16:14:~/test/123
=> git update-index --no-assume-unchanged f
85 gewang@LM-SHC-00355679@13:17:50:~/test/123
=> git diff
diff --git a/f b/f
index 541d3ff..6b239cf 100644
--- a/f
+++ b/f
@@ -5,3 +5,5 @@ abcaaa
aaa
dfadfaa
dlfaldf
+#####
+-------
#!/usr/bin/ruby
# Author: loveky <ylzcylx#gmail.com>
# Blog : http://loveky2012.blogspot.com
# This script will parse the given index file and output all entries in it.
# run 'parse_index_file.rb -h' for help message
$: << File.dirname(__FILE__)
require 'bindata'
require 'optparse'
require 'IndexEntry'
STANDARD_SIGNATURE = 'DIRC'
entry_count = 1
begin
options = {}
opts = OptionParser.new do |opts|
opts.banner = "Parse the index file and show you what is there"
opts.on('-f FILE ','--file FILE', 'Path to the index file') do |value|
options[:file] = value
end
opts.on_tail("-h", "--help", "Show this message") do
puts opts
exit
end
end.parse!
raise ArgumentError, "No index file given!" if options[:file] == nil
File.open(options[:file], "rb") do |fd|
SIGNATURE = fd.read(4)
raise RuntimeError, "Not an index file!" if SIGNATURE != STANDARD_SIGNATURE
VERSION = fd.read(4).unpack("N")[0]
ENTRIES_NUMBER = fd.read(4).unpack("N")[0]
puts "Index version : #{VERSION}"
puts "Entries number: #{ENTRIES_NUMBER}"
ENTRIES_NUMBER.times do
entry = IndexEntry.read(fd)
puts "Found file: " + entry.path
puts " SHA1 : " + entry.sha1.unpack("H40").join
puts " stage : #{entry.flags << 2 >> 14}"
puts " ctime : " + Time.at(entry.ctime_s + entry.ctime_ns * 10**-9).strftime('%Y-%m-%d %H:%M:%S.%9N')
puts " mtime : " + Time.at(entry.mtime_s + entry.mtime_ns * 10**-9).strftime('%Y-%m-%d %H:%M:%S.%9N')
puts " size : #{entry.file_size}"
if (fd.pos - 12) % 8 != 0
fd.seek(8 - ((fd.pos - 12) % 8), IO::SEEK_CUR)
end
end
end
rescue => ex
puts "#{ex.class}: #{ex.message}"
end
GIT index format
================
= The git index file has the following format
All binary numbers are in network byte order. Version 2 is described
here unless stated otherwise.
- A 12-byte header consisting of
4-byte signature:
The signature is { 'D', 'I', 'R', 'C' } (stands for "dircache")
4-byte version number:
The current supported versions are 2 and 3.
32-bit number of index entries.
- A number of sorted index entries (see below).
- Extensions
Extensions are identified by signature. Optional extensions can
be ignored if GIT does not understand them.
GIT currently supports cached tree and resolve undo extensions.
4-byte extension signature. If the first byte is 'A'..'Z' the
extension is optional and can be ignored.
32-bit size of the extension
Extension data
- 160-bit SHA-1 over the content of the index file before this
checksum.
== Index entry
Index entries are sorted in ascending order on the name field,
interpreted as a string of unsigned bytes (i.e. memcmp() order, no
localization, no special casing of directory separator '/'). Entries
with the same name are sorted by their stage field.
32-bit ctime seconds, the last time a file's metadata changed
this is stat(2) data
32-bit ctime nanosecond fractions
this is stat(2) data
32-bit mtime seconds, the last time a file's data changed
this is stat(2) data
32-bit mtime nanosecond fractions
this is stat(2) data
32-bit dev
this is stat(2) data
32-bit ino
this is stat(2) data
32-bit mode, split into (high to low bits)
4-bit object type
valid values ina binary are 1000 (regular file), 1010 (symbolic link)
and 1110 (gitlink)
3-bit unused
9-bit unix permission. Only 0755 and 0644 are valid for regular files.
Symbolic links and gitlinks have value 0 in this field.
32-bit uid
this is stat(2) data
32-bit gid
this is stat(2) data
32-bit file size
This is the on-disk size from stat(2), truncated to 32-bit.
160-bit SHA-1 for the represented object
A 16-bit 'flags' field split into (high to low bits)
1-bit assume-valid flag
1-bit extended flag (must be zero in version 2)
2-bit stage (during merge)
12-bit name length if the length is less than 0xFFF; otherwise 0xFFF
is stored in this field.
(Version 3) A 16-bit field, only applicable if the "extended flag"
above is 1, split into (high to low bits).
1-bit reserved for future
1-bit skip-worktree flag (used by sparse checkout)
1-bit intent-to-add flag (used by "git add -N")
13-bit unused, must be zero
Entry path name (variable length) relative to top level directory
(without leading slash). '/' is used as path separator. The special
path components ".", ".." and ".git" (without quotes) are disallowed.
Trailing slash is also disallowed.
The exact encoding is undefined, but the '.' and '/' characters
are encoded in 7-bit ASCII and the encoding cannot contain a NUL
byte (iow, this is a UNIX pathname).
(Version 4) In version 4, the entry path name is prefix-compressed
relative to the path name for the previous entry (the very first
entry is encoded as if the path name for the previous entry is an
empty string). At the beginning of an entry, an integer N in the
variable width encoding (the same encoding as the offset is encoded
for OFS_DELTA pack entries; see pack-format.txt) is stored, followed
by a NUL-terminated string S. Removing N bytes from the end of the
path name for the previous entry, and replacing it with the string S
yields the path name for this entry.
1-8 nul bytes as necessary to pad the entry to a multiple of eight bytes
while keeping the name NUL-terminated.
(Version 4) In version 4, the padding after the pathname does not
exist.
== Extensions
=== Cached tree
Cached tree extension contains pre-computed hashes for trees that can
be derived from the index. It helps speed up tree object generation
from index for a new commit.
When a path is updated in index, the path must be invalidated and
removed from tree cache.
The signature for this extension is { 'T', 'R', 'E', 'E' }.
A series of entries fill the entire extension; each of which
consists of:
- NUL-terminated path component (relative to its parent directory);
- ASCII decimal number of entries in the index that is covered by the
tree this entry represents (entry_count);
- A space (ASCII 32);
- ASCII decimal number that represents the number of subtrees this
tree has;
- A newline (ASCII 10); and
- 160-bit object name for the object that would result from writing
this span of index as a tree.
An entry can be in an invalidated state and is represented by having
-1 in the entry_count field. In this case, there is no object name
and the next entry starts immediately after the newline.
The entries are written out in the top-down, depth-first order. The
first entry represents the root level of the repository, followed by the
first subtree---let's call this A---of the root level (with its name
relative to the root level), followed by the first subtree of A (with
its name relative to A), ...
=== Resolve undo
A conflict is represented in the index as a set of higher stage entries.
When a conflict is resolved (e.g. with "git add path"), these higher
stage entries will be removed and a stage-0 entry with proper resoluton
is added.
When these higher stage entries are removed, they are saved in the
resolve undo extension, so that conflicts can be recreated (e.g. with
"git checkout -m"), in case users want to redo a conflict resolution
from scratch.
The signature for this extension is { 'R', 'E', 'U', 'C' }.
A series of entries fill the entire extension; each of which
consists of:
- NUL-terminated pathname the entry describes (relative to the root of
the repository, i.e. full pathname);
- Three NUL-terminated ASCII octal numbers, entry mode of entries in
stage 1 to 3 (a missing stage is represented by "0" in this field);
and
- At most three 160-bit object names of the entry in stages from 1 to 3
(nothing is written for a missing stage).
git diff topic master (1) git diff topic..master (2) git diff topic...master (3)
git hash-object path/to/file或者直接使用几个shell命令生成：
(echo -e -n "blob $(wc -c path/to/file | awk '{print $1}')\0" ; cat path/to/file) | shasum
git whatchanged -m -- path/to/file
#!/usr/bin/ruby
# Author: loveky <ylzcylx@gmail.com>
# Blog : http://loveky2012.blogspot.com
#Usage: find_it_in_history.rb --file <file> --repo <path/to/repo> --path_in_repo <file/path/in/repo>
require 'digest/sha1'
require 'optparse'
found = false
commit = nil
options = {}
OptionParser.new do |opts|
opts.banner = "Find the commit who first introduced the specified version of a file"
opts.on('--file FILE', 'Which file to check') do |value|
options[:file] = value
end
opts.on('--repo REPO', 'which repo to check') do |value|
options[:repo] = value
end
opts.on('--path_in_repo PATH', 'the path of the file in repo') do |value|
options[:path_in_repo] = value
end
end.parse!
file_content = File.open(options[:file]) {|f| f.read}
file_sha1 = Digest::SHA1.hexdigest("blob #{file_content.length}\0" + file_content)
puts("#{options[:file]} => #{file_sha1}")
Dir.chdir(options[:repo])
IO.popen("git whatchanged --oneline -m -- #{options[:path_in_repo]}") do |git_whatchanged|
git_whatchanged.each_line do |line|
if line[0,1] == ':'
new_blob = (/\.\.\. ([0-9a-fA-F]{7})\.\.\./.match(line))[1]
if new_blob == file_sha1[0,7]
puts "Found blob(#{file_sha1[0,7]}) in commit " + commit
found = true
elsif found == true
exit 0
end
else
commit = line[0,7]
end
end
end
error: Your local changes to the following files would be overwritten by checkout: b Please, commit your changes or stash them before you can switch branches. Aborting组织你切换分支。
git stath save [message]
git stash list
git stash apply [--index] [stash]
git stash pop [--index] [stash]
git stash drop [stash]
git stash clear
gewang@LM-SHC-00355679@17:01:40:~/test/TryOurInternalGithub => git log --oneline -1 # 查看当前所在commit ab2d6ee 2nd commit gewang@LM-SHC-00355679@16:34:14:~/test/TryOurInternalGithub => find .git/objects/ .git/objects/ .git/objects//info .git/objects//info/packs .git/objects//pack .git/objects//pack/pack-37b8c10ba135fb7e9166a0ea483ab9597b15d039.idx .git/objects//pack/pack-37b8c10ba135fb7e9166a0ea483ab9597b15d039.pack gewang@LM-SHC-00355679@16:34:17:~/test/TryOurInternalGithub => git tag tag1 # 创建轻量级的tag1 gewang@LM-SHC-00355679@16:34:23:~/test/TryOurInternalGithub => find .git/objects/ # 没有新的object生成 .git/objects/ .git/objects//info .git/objects//info/packs .git/objects//pack .git/objects//pack/pack-37b8c10ba135fb7e9166a0ea483ab9597b15d039.idx .git/objects//pack/pack-37b8c10ba135fb7e9166a0ea483ab9597b15d039.pack gewang@LM-SHC-00355679@16:34:26:~/test/TryOurInternalGithub => git tag tag2 -m "tag2" # 创建一个带说明的提交 gewang@LM-SHC-00355679@16:34:42:~/test/TryOurInternalGithub => find .git/objects/ # 生成了一个新的object 84458d .git/objects/ .git/objects//84 .git/objects//84/458d8d078307134b8f6712d84c07f438ba6657 .git/objects//info .git/objects//info/packs .git/objects//pack .git/objects//pack/pack-37b8c10ba135fb7e9166a0ea483ab9597b15d039.idx .git/objects//pack/pack-37b8c10ba135fb7e9166a0ea483ab9597b15d039.pack
gewang@LM-SHC-00355679@16:59:23:~/test/TryOurInternalGithub => ls .git/refs/tags/ tag1 tag2接着查看两者的内容：
gewang@LM-SHC-00355679@17:00:34:~/test/TryOurInternalGithub => cat .git/refs/tags/tag1 ab2d6eea3cde6b1fac1784a6afb19a552a78689e gewang@LM-SHC-00355679@17:01:14:~/test/TryOurInternalGithub => cat .git/refs/tags/tag2 84458d8d078307134b8f6712d84c07f438ba6657
gewang@LM-SHC-00355679@17:04:17:~/test/TryOurInternalGithub => git cat-file -t 84458d8d078307134b8f6712d84c07f438ba6657 tag gewang@LM-SHC-00355679@17:04:22:~/test/TryOurInternalGithub => git cat-file -p 84458d8d078307134b8f6712d84c07f438ba6657 object ab2d6eea3cde6b1fac1784a6afb19a552a78689e type commit tag tag2 tagger Michael Wang可以看到新生成的object的类型是tag（这是git四个基本object类型中的一种，其他三种是commit，tree，blob）。可以看到这个object记录的5条信息，它指向了一个id为ab2d6eea3的对象，这个对象的类型为commit，这个tag的名字叫tag2，打tag的username是Michael，当天给的message是“tag2”。Tue Aug 14 16:34:42 2012 +0800 tag2
gewang@LM-SHC-00355679@17:04:25:~/test/TryOurInternalGithub => git push Everything up-to-dategit提示我们所有的refs都已经up-to-date，表示git默认不会推送本地tag到server端，必须明确指定要推送的tag：
gewang@LM-SHC-00355679@17:16:24:~/test/TryOurInternalGithub => git push origin tag1 Total 0 (delta 0), reused 0 (delta 0) To git@github.scm.corp.ebay.com:gewang/TryOurInternalGithub.git * [new tag] tag1 -> tag1 gewang@LM-SHC-00355679@17:17:38:~/test/TryOurInternalGithub => git push origin tag2 Counting objects: 1, done. Writing objects: 100% (1/1), 158 bytes, done. Total 1 (delta 0), reused 0 (delta 0) To git@github.scm.corp.ebay.com:gewang/TryOurInternalGithub.git * [new tag] tag2 -> tag2在上边的例子中可以看到推送tag2时，向server端写了1个object，而tag1则没有，这也印证了2者的区别。
gewang@LM-SHC-00355679@17:20:45:~/test/TryOurInternalGithub => git tag -d tag1 Deleted tag 'tag1' (was ab2d6ee) gewang@LM-SHC-00355679@17:20:54:~/test/TryOurInternalGithub => git tag -d tag2 Deleted tag 'tag2' (was 84458d8) gewang@LM-SHC-00355679@17:20:54:~/test/TryOurInternalGithub => git pull remote: Counting objects: 1, done. remote: Total 1 (delta 0), reused 1 (delta 0) Unpacking objects: 100% (1/1), done. From github.scm.corp.ebay.com:gewang/TryOurInternalGithub * [new tag] tag1 -> tag1 * [new tag] tag2 -> tag2可以看到默认清空下，git pull会将server端的tag获取到本地。
git checkout -- [filename]
git reset HEAD -- [filename]如果还想重置工作区，可以继续：
git checkout -- [filename]
A---B---C---D---E---F---G---H
|
master
子情形1. 要撤销最近1个commit,要撤销H。git reset --hard G或
git revert H二者区别在于git reset不会产生新的提交，而是将分支指向指定的commit，生成的提交历史为：
A---B---C---D---E---F---G---H
|
master
而git revert会产生一个新的提交，生成的提交历史为：A---B---C---D---E---F---G---H---I
|
master
git rebase --onto D G^ H
git reset --hard HEAD
git revert -m [parent-number] [refs]-m指定要采用哪条主线（编号从1开始）。
git fsck dangling blob 9daeafb9864cf43055ae93beb0afd6c7d144bfa4 #有一个blob对象，没有被任何commit引用到。但是依旧占用磁盘空间，需要清理。 git fsck --root --tags tagged commit b40c14f880c04fefcdce1328a2d6a537ed64b182 (test_tag1) in 00311b3f18af6306df2e5843d13a901681b677ef #一个tag tagged commit f62a94635be5b72c9778a04aea116f6b4349eb61 (test_tag2) in 4de836025102abda82c0fd544a8725c82c46752f #另一个tag root 63a763ead83edabcadac4f62a08b0d39b0d719b4 #当前repo的历史中第一次commit。 dangling blob 9daeafb9864cf43055ae93beb0afd6c7d144bfa4
git repack -a -d git repack -A -d两者的区别在于：
=> git log --oneline -3 b841691 Merge branch 'test' of github.scm.corp.ebay.com:gewang/TryOurInternalGithub ec55218 1 on test c1b13cb dd => touch test => echo test >> test => git add test => git commit -m "test git fsck" [master d2d0bfa] test git fsck 1 files changed, 1 insertions(+), 0 deletions(-) create mode 100644 test => git reset --hard HEAD^ #rollback到之前一个commit，制造一个dangling commit。 HEAD is now at b841691 Merge branch 'test' of github.scm.corp.ebay.com:gewang/TryOurInternalGithub => git fsck #因为刚刚的commit现在还可以通过reflog引用到，所以fsck并不认为它是unreachable。 => git fsck --no-reflog #忽略reflog就可以看到 dangling commit d2d0bfa2ee4dfe767862cb441595db9748d8beab => git reflog expire --expire=now --all #删除reflog => git fsck #成功制造了一个dangling commit。 dangling commit d2d0bfa2ee4dfe767862cb441595db9748d8beab => git prune #删掉它！ => git fsck
=> git log --oneline -3 b841691 Merge branch 'test' of github.scm.corp.ebay.com:gewang/TryOurInternalGithub ec55218 1 on test c1b13cb dd => touch test => echo test >> test => git add test => git commit -m "test fsck, prune and repack" [master 09f3015] test fsck, prune and repack 1 files changed, 1 insertions(+), 0 deletions(-) create mode 100644 test => git repack #首先将新创建的commit打包。 Counting objects: 3, done. Delta compression using up to 8 threads. Compressing objects: 100% (2/2), done. Writing objects: 100% (3/3), done. Total 3 (delta 0), reused 0 (delta 0) => git reset --hard HEAD^ HEAD is now at b841691 Merge branch 'test' of github.scm.corp.ebay.com:gewang/TryOurInternalGithub => git fsck => git fsck --no-reflog dangling commit 09f3015743b00805e100259b9b4b0c230236a891 => git reflog expire --expire=now --all => git fsck #制造了一个dangling commit。 dangling commit 09f3015743b00805e100259b9b4b0c230236a891 => git prune => git fsck #prune无法删除已经pack的object。 dangling commit 09f3015743b00805e100259b9b4b0c230236a891 => git repack -a -d #reapck -a -d 直接删除。 Counting objects: 173, done. Delta compression using up to 8 threads. Compressing objects: 100% (94/94), done. Writing objects: 100% (173/173), done. Total 173 (delta 59), reused 173 (delta 59) => git fsck
=> git log --oneline -3 b841691 Merge branch 'test' of github.scm.corp.ebay.com:gewang/TryOurInternalGithub ec55218 1 on test c1b13cb dd => touch test => echo test >> test => git add test => git commit -m "test fsck, prune and repack -A" [master 8df4fa5] test fsck, prune and repack -A 1 files changed, 1 insertions(+), 0 deletions(-) create mode 100644 test => git repack Counting objects: 3, done. Delta compression using up to 8 threads. Compressing objects: 100% (2/2), done. Writing objects: 100% (3/3), done. Total 3 (delta 0), reused 0 (delta 0) => find .git/objects/ # 当前database中的文件。 .git/objects/ .git/objects//8d .git/objects//8d/f4fa5b683a6c2614d0bb5f6a9bbd0df6e76ebb .git/objects//9d .git/objects//9d/aeafb9864cf43055ae93beb0afd6c7d144bfa4 .git/objects//e6 .git/objects//e6/a38484a68f1d818090516266a1fe5115bedb2d .git/objects//info .git/objects//info/packs .git/objects//pack .git/objects//pack/pack-f82243c549f6e21d59eb4b3cd90c1f7ea4bc2b2f.idx .git/objects//pack/pack-f82243c549f6e21d59eb4b3cd90c1f7ea4bc2b2f.pack .git/objects//pack/pack-ff6a31c9b76b7a762bf76eb2500048a55e0e076d.idx .git/objects//pack/pack-ff6a31c9b76b7a762bf76eb2500048a55e0e076d.pack => git gc # 清理一下。 Counting objects: 176, done. Delta compression using up to 8 threads. Compressing objects: 100% (96/96), done. Writing objects: 100% (176/176), done. Total 176 (delta 60), reused 175 (delta 59) => find .git/objects/ #现在干净多了。 .git/objects/ .git/objects//info .git/objects//info/packs .git/objects//pack .git/objects//pack/pack-25320b3227fb4b00d05585542643651019b1a041.idx .git/objects//pack/pack-25320b3227fb4b00d05585542643651019b1a041.pack => git reset --hard HEAD^ HEAD is now at b841691 Merge branch 'test' of github.scm.corp.ebay.com:gewang/TryOurInternalGithub => git fsck => git fsck --no-reflog dangling commit 8df4fa5b683a6c2614d0bb5f6a9bbd0df6e76ebb => git reflog expire --expire=now --all => git fsck #制造dangling commit。 dangling commit 8df4fa5b683a6c2614d0bb5f6a9bbd0df6e76ebb => git prune => git fsck dangling commit 8df4fa5b683a6c2614d0bb5f6a9bbd0df6e76ebb => git repack -A -d #这次使用-A Counting objects: 173, done. Delta compression using up to 8 threads. Compressing objects: 100% (94/94), done. Writing objects: 100% (173/173), done. Total 173 (delta 59), reused 172 (delta 59) => git fsck #这货还在 dangling commit 8df4fa5b683a6c2614d0bb5f6a9bbd0df6e76ebb => find .git/objects/ #对应的松散对象也出现啦。 .git/objects/ .git/objects//8d .git/objects//8d/f4fa5b683a6c2614d0bb5f6a9bbd0df6e76ebb .git/objects//9d .git/objects//9d/aeafb9864cf43055ae93beb0afd6c7d144bfa4 .git/objects//e6 .git/objects//e6/a38484a68f1d818090516266a1fe5115bedb2d .git/objects//info .git/objects//info/packs .git/objects//pack .git/objects//pack/pack-ff6a31c9b76b7a762bf76eb2500048a55e0e076d.idx .git/objects//pack/pack-ff6a31c9b76b7a762bf76eb2500048a55e0e076d.pack
263 gewang@LM-SHC-00355679@13:55:04:~/test/show => git merge master Auto-merging test CONFLICT (content): Merge conflict in test Automatic merge failed; fix conflicts and then commit the result. 264 gewang@LM-SHC-00355679@13:55:07:~/test/show => git ls-files -s 100644 e69de29bb2d1d6434b8b29ae775ad8c2e48c5391 0 aaa 100644 388ddf68417917d4c0e0faa74432c1c2e74d572e 1 test 100644 733205e05f85d7b51b96cbef2938d61bf304798b 2 test 100644 23bc1c902ffde28525f215cd2bfc44b6f4222709 3 test可以看到test文件出现了3个stage的状态，分别为1，2，3。而没有出现冲突的文件的stage状态为0.
git show :1:test # 查看冲突文件的common ancester版本 git show :2:test # 查看本地branch中的版本 git show :3:test # 查看远程branch中的版本
name = case x
when 1; "one"
when 2; "two"
when 3; "three"
else "many"
end
name = case
when 1 === x; "one"
when 2 === x; "two"
when 3 === x; "three"
else "many"
end
puts case x when String then "string" when Numeric then "number" when TrueClass, FalseClass then "boolean" else "other" end
while line=gets.chomp do
case line
when /^\s*#/
next
when /^quit$/i
break
else
puts line.reverse
end
end
git filter-branch [--env-filter这个命令会按照指定的方式（一系列过滤器，filter）修改给定的commit，几乎可以针对历史commit执行你想要的任何操作。比如，从历史中删除某个文件，修改commit message等。] [--tree-filter ] [--index-filter ] [--parent-filter ] [--msg-filter ] [--commit-filter ] [--tag-name-filter ] [--subdirectory-filter ] [--prune-empty] [--original ] [-d ] [-f | --force] [--] [ ...]
--env-filter --tree-filter --index-filter --parent-filter --msg-filter --commit-filter --tag-name-filter --subdirectory-filter当同时指定多个filter时，会按照上述列表中列出的先后顺序执行相应filter。在执行由filter设置的操作时，git会自动设置以下系统变量：
$GIT_COMMIT $GIT_AUTHOR_NAME $GIT_AUTHOR_EMAIL $GIT_AUTHOR_DATE $GIT_COMMITTER_NAME $GIT_COMMITTER_EMAIL $GIT_COMMITTER_DATE这些变量包含了改写操作执行前当前commit的相关信息。
git filter-branch --tree-filter 'rm filename' HEAD
git filter-branch --index-filter 'git rm --cached --ignore-unmatch filename' HEAD
With --no-ff Generate a merge commit even if the merge resolved as a fast-forward.意思是即使此次merge可以fast-forward，也要创建一个新的commit。
git checkout master此时log如下：
git merge test
git merge --no-ff test效果如图
1. 如果为当前分支设置了<remote>，即由配置branch.<branchname>.remote给出了远程版本库代号，则不带参数执行git push相当于执行了git push <remote>。当不带任何参数执行git pull命令时，实际执行过程是：
2. 如果没有为当前分支设置<remote>，则不带参数执行git push相当于执行了git push origin。
3. 要推送的远程版本库的URL由remote.<remote>.pushurl给出。如果没有配置，则使用remote.<remote>.url配置的URL地址。
4. 如果为注册的远程版本库设置了push参数，即通过remote.<remote>.push配置了一个引用表达式，则使用该引用表达式执行推送。
5. 否则使用“:”作为引用表达式。该表达式的含义是同名分支推送，即对所有在远程版本库中有同名分支的本地分支执行推送。
1. 如果为当前branch设置了<remote>，即由配置branch.<branchname>.remote出了远程版本库代号，则不带参数执行git pull相当于执行了git pull <remote>。下面说说自己的理解：
2. 如果没有为当前分支设置<remote>，则不带参数执行git pull相当于执行了git pull origin
3. 要获取的远程版本库的URL地址由remote.<remote>.url给出。
4. 如果为注册的远程版本库设置了fetch参数，即通过remote.<remote>.fetch配置了一个引用表达式,则使用该引用表达式执行获取操作
5. 接下来要确定合并分支。如果设定了branch.<branchname>.merge，则对其设定的分支执行合并，否则报错退出。
SELECT * FROM PushEvent;
SELECT * FROM PushEvent WHERE event_id < 205530;
SELECT max(event_id) FROM PushEvent;
SELECT * FROM PushEvent WHERE strftime('%s', create_at) < strftime('%s', "2012-07-26");
SELECT * FROM PushEvent WHERE
strftime('%s', created_at) < strftime('%s', "2012-07-26 07:11:00")
AND
strftime('%s', created_at) > strftime('%s', "2012-07-26 07:06:00");
sqlite3 events.sqlite3这会创建一个新的，名为events.sqlite3的空数据文件。接着创建一张测试表：
CREATE TABLE PushEvent ( event_id INTEGER PRIMARY KEY, created_at text, actor_login text, repo_name text, payload_size INTEGER DEFAULT NULL );这样我们已经在新的数据文件中创建了一张测试表，包含5个字段。
require 'sqlite3'
begin
db = SQLite3::Database.open "../db/events.sqlite3"
rescue SQLite3::Exception => e
puts "Cannot open SQLite3 db"
puts e
end
db.execute "INSERT INTO PushEvent VALUES(205205, '2012-07-25T08:21:34Z',
'ju', 'zh/Registrat', 1)"
db.close
gem install sqlite3
require 'yajl'
require 'em-http'
require 'em-http/middleware/json_response'
$latest_event_id = 0;
$base_api_url = "https://内部github链接";
$push_event_count = 0
$push_event_commit_count = 0
$create_event_repo_count = 0
$create_event_branch_count = 0
$create_event_tag_count = 0
EM.run do
stop = Proc.new do
puts "Terminating event crawler"
puts "Following events occurs during monitor:"
puts "Push #{$push_event_count}"
puts "Commit #{$push_event_commit_count}"
puts "Repo creation #{$create_event_repo_count}"
puts "Branch creation #{$create_event_branch_count}"
puts "Tag creation #{$create_event_tag_count}"
EM.stop
end
Signal.trap("INT", &stop)
Signal.trap("TERM", &stop)
process = Proc.new do
req = EM::HttpRequest.new($base_api_url + "/events").get
req.callback do
latest_page = Yajl::Parser.parse(req.response)
new_events = latest_page.reject { |e| e['id'].to_i <= $latest_event_id }
new_events_id = latest_page.collect { |e| e['id'].to_i }
$latest_event_id = new_events_id.max
new_events.each do |event|
if event['type'] == "PushEvent" then
$push_event_count += 1
$push_event_commit_count += event['payload']['size']
end
if event['type'] == "CreateEvent" then
case event['payload']
when "repository" then $create_event_repo_count += 1
when "branch" then $create_event_branch_count += 1
when "tag" then $create_event_tag_count += 1
end
end
end
puts "Found #{new_events.size} new events"
if new_events.size >= 25
EM.add_timer(1.5, &process)
end
end
end
EM.add_periodic_timer(12, &process)
end