Git - calculate how many lines of code were added/changed by someone

gitstats.sh

# Run this in the project repo from the command-line
# http://stackoverflow.com/a/4593065/99923

git log --shortstat --author "Xeoncross" --since "2 weeks ago" --until "1 week ago" | grep "files changed" | awk '{files+=$1; inserted+=$4; deleted+=$6} END {print "files changed", files, "lines inserted:", inserted, "lines deleted:", deleted}'

You can replace grep "files changed" | awk '{… with awk '/files changed/ {..., that way one less process is needed.

Thanks a lot for this!
Expanded on your idea and came up with this to count across projects:

for i in */.git
do
    (cd ${i%/*}
    git log --shortstat --author "Xeoncross" | awk '
        BEGIN { f=0 ; i=0 ; d=0 }
        /files? changed/ {f+=$1; i+=$4; d+=$6}
        END { printf("files changed: %4i - lines inserted: %6i lines deleted: %6i - %s\n", f, i, d, p) }' p=${i%/*}
    )
done | awk '
    { f+=$3 ; i+=$7 ; d+=$10 ; print }
    END { print "----" ; printf("files changed: %4i - lines inserted: %6i lines deleted: %6i - %s\n", f, i, d, "Total") }'

Also updated "files changed" to "files? changed" which will match both "file changed" and "files changed".

Just another improvement on this:

author="YourAuthorHere"
for i in */.git
do
    (cd ${i%/*}
    git log --shortstat --author $author | awk '
        BEGIN { f=0 ; i=0 ; d=0 }
        /files? changed/ {f+=$1; i+=$4; d+=$6}
        END { printf("files changed: %4i - lines inserted: %6i lines deleted: %6i - %s\n", f, i, d, p) }' p=${i%/*}
    )
done | awk '
    { f+=$3 ; i+=$7 ; d+=$10 ; print }
    END { print "----" ; printf("files changed: %4i - lines inserted: %6i lines deleted: %6i - %s\n", f, i, d, "Total") }'

or just make a function and put into bash profile

function gline() {
	cd path/to/your/repo
	git log --shortstat --author $1 --since "10 years ago" --until "1 week ago" | grep "files changed" | awk '{files+=$1; inserted+=$4; deleted+=$6} END {print "files changed", files, "lines inserted:", inserted, "lines deleted:", deleted}'
}

and then you can do
gline YourName

It misses commits where only 1 file was changed:
1 file changed, 3 insertions(+), 2 deletions(-)

could modify grep part as
egrep "file[s]* changed"

Very good try. However, the command does not produce correct results.
First, it can misinterpret deletions as additions.
Please consider the following stat:
2 files changed, 2 deletions(-)
In case a commit does not have any additions, but only removals, as the one shown above, the number of lines removed will be added to the total of the lines added.
Given the example provided above, the command will report that 2 lines were added, and 0 were deleted, while in fact, it was the opposite.
Second, it misses the commits where 1 file was changed as mentioned by @kirhgoff.

To address @lack3r 's valid concerns, you can insert '0 insertions ', e.g.: sed 's/changed, \([0-9]\+ deletions\)/changed, 0 insertions(+), \1/g'.

Together with @kirhgoff 's modified grep, this gives us:

git log --shortstat --author "user"  \
    | egrep "file[s] changed" \
    | sed 's/changed, \([0-9]\+ deletions\)/changed, 0 insertions(+), \1/g' \
    | awk '{files+=$1; inserted+=$4; deleted+=$6} END {print "files changed", files, "lines inserted:", inserted, "lines deleted:", deleted}'

@neuged: Changes to your command:

• Added missing asterisk to egrep
• added since and until parameters

git log --shortstat --author "username"  --since "5 days ago" --until "today" \
    | egrep "file[s]* changed" \
    | sed 's/changed, \([0-9]\+ deletions\)/changed, 0 insertions(+), \1/g' \
    | awk '{files+=$1; inserted+=$4; deleted+=$6} END {print "files changed", files, "lines inserted:", inserted, "lines deleted:", deleted}'

How do I make an alias of this? Because we use both ' and ", I do not know a syntax to get a valid command. This is what I have now:

git config --global alias.my-contribution "!git log ..."

building on the previous solutions, if you want to skip certain files you can add -- ':!pattern'

git log --stat 0000000..HEAD -- ':!*test.go' | rg "files changed" | awk ...