cmd/go: set user and email in test-local git repos

Some of the builders cannot infer user and email from the builder hostname.

Change-Id: I27e5d011fa1471f27763b6b7fa1bf59e418b925c
Reviewed-on: https://team-review.git.corp.google.com/c/376739
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Reviewed-on: https://go-review.googlesource.com/c/154107
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Dmitri Shuralyov <dmitshur@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/cmd/go/testdata/script/get_brace.txt

@@ -3,11 +3,15 @@
 # Set up some empty repositories.
 cd $WORK/_origin/foo
 exec git init
+exec git config user.name 'Nameless Gopher'
+exec git config user.email 'nobody@golang.org'
 exec git commit --allow-empty -m 'create master branch'
 
 cd $WORK
 cd '_origin/{confusing}'
 exec git init
+exec git config user.name 'Nameless Gopher'
+exec git config user.email 'nobody@golang.org'
 exec git commit --allow-empty -m 'create master branch'
 
 # Clone the empty repositories into GOPATH.

src/cmd/go/testdata/script/get_dotfiles.txt

@@ -3,10 +3,14 @@
 # Set up a benign repository and a repository with a dotfile name.
 cd $WORK/_origin/foo
 exec git init
+exec git config user.name 'Nameless Gopher'
+exec git config user.email 'nobody@golang.org'
 exec git commit --allow-empty -m 'create master branch'
 
 cd $WORK/_origin/.hidden
 exec git init
+exec git config user.name 'Nameless Gopher'
+exec git config user.email 'nobody@golang.org'
 exec git commit --allow-empty -m 'create master branch'
 
 # Clone the empty repositories into GOPATH.

src/cmd/go/testdata/script/get_unicode.txt

@@ -1,23 +1,32 @@
 [!exec:git] skip
 
+# Construct a repository that imports a non-ASCII path.
 cd $WORK/_origin/example.com/unicode
 exec git init
+exec git config user.name 'Nameless Gopher'
+exec git config user.email 'nobody@golang.org'
 exec git add unicode.go
 exec git commit -m 'add unicode.go'
 
+# Clone the repo into GOPATH so that 'go get -u' can find it.
 mkdir $GOPATH/src/example.com/unicode
 cd $GOPATH/src/example.com/unicode
 exec git clone $WORK/_origin/example.com/unicode .
 
+# Construct the imported repository.
 cd $WORK/_origin/example.com/испытание
 exec git init
+exec git config user.name 'Nameless Gopher'
+exec git config user.email 'nobody@golang.org'
 exec git add испытание.go
 exec git commit -m 'add испытание.go'
 
+# Clone that repo into GOPATH too.
 mkdir $GOPATH/src/example.com/испытание
 cd $GOPATH/src/example.com/испытание
 exec git clone $WORK/_origin/example.com/испытание .
 
+# Upgrading the importer should pull from the non-ASCII repo.
 cd $GOPATH
 go get -u example.com/unicode